Annual report pursuant to Section 13 and 15(d)

Schedule III (Details)

v2.4.0.8
Schedule III (Details) (USD $)
12 Months Ended
Dec. 31, 2013
units
sqft
Dec. 31, 2012
sqft
Dec. 31, 2011
sqft
Real Estate and Accumulated Depreciation [Line Items]      
Initial Cost, Land $ 476,688,000 [1]    
Initial Cost, Buildings and Improvements 1,264,555,000 [1]    
Net Improvements (Retirement) since Acquisition 548,266,000    
Gross Amounts at Which Carried at December 31, 2011, Land 490,036,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 1,799,473,000    
Gross Amounts at Which Carried at December 31, 2011, Total 2,289,509,000 [2] 2,529,131,000 2,449,872,000
Accumulated Depreciation at December 31, 2011 611,408,000 610,536,000 535,732,000
Net Rentable Square Feet 9,711,000 [3]    
Units 2,674    
Secured Debt 294,671,000 319,025,000  
Mortgage notes payable 294,671,000 342,970,000  
Real estate, federal income tax basis 1,939,300,000    
Area of land 1,599,000 134,000 3,272,000
Land Available for Development 3,600,000    
Development in Process 61,315,000 45,270,000  
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, beginning of period 2,529,131,000 2,449,872,000 2,443,127,000
Property acquisitions 47,444,000 [4] 47,772,000 [4] 352,658,000 [4]
Improvements 71,127,000 [4] 59,664,000 [4] 36,386,000 [4]
Impairment write-down 0 (2,097,000) (16,416,000)
Write-off of disposed assets (2,017,000) (1,450,000) (1,648,000)
Property sales (356,176,000) (24,630,000) (364,235,000)
Balance, end of period 2,289,509,000 [2] 2,529,131,000 2,449,872,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, beginning of period 610,536,000 535,732,000 538,786,000
Depreciation 80,510,000 84,949,000 84,167,000
Impairment write-down 0 0 (1,291,000)
Write-off of disposed assets (1,404,000) (1,124,000) (1,648,000)
Property sales (78,234,000) (9,021,000) (84,282,000)
Balance, end of period 611,408,000 610,536,000 535,732,000
Multifamily Properties [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Initial Cost, Land 79,524,000 [1]    
Initial Cost, Buildings and Improvements 124,275,000 [1]    
Net Improvements (Retirement) since Acquisition 234,209,000    
Gross Amounts at Which Carried at December 31, 2011, Land 103,165,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 334,843,000    
Gross Amounts at Which Carried at December 31, 2011, Total 438,008,000 [2]    
Accumulated Depreciation at December 31, 2011 132,271,000    
Net Rentable Square Feet 2,278,000 [3]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 438,008,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 132,271,000    
3801 Connecticut [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC [5]    
Initial Cost, Land 420,000 [1],[5]    
Initial Cost, Buildings and Improvements 2,678,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 9,715,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 420,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 12,393,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 12,813,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 8,905,000 [5]    
Year of Construction Jan. 01, 1951 [5]    
Date of Acquisition Jan. 01, 1963 [5]    
Net Rentable Square Feet 179,000 [3]    
Units 307    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 12,813,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 8,905,000 [5]    
Roosevelt Towers [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 336,000 [1]    
Initial Cost, Buildings and Improvements 1,996,000 [1]    
Net Improvements (Retirement) since Acquisition 10,995,000    
Gross Amounts at Which Carried at December 31, 2011, Land 336,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 12,991,000    
Gross Amounts at Which Carried at December 31, 2011, Total 13,327,000 [2]    
Accumulated Depreciation at December 31, 2011 7,719,000    
Year of Construction Jan. 01, 1964    
Date of Acquisition May 01, 1965    
Net Rentable Square Feet 170,000 [3]    
Units 191    
Depreciation Life 40 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 13,327,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 7,719,000    
Country Club Towers [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 299,000 [1]    
Initial Cost, Buildings and Improvements 2,562,000 [1]    
Net Improvements (Retirement) since Acquisition 15,088,000    
Gross Amounts at Which Carried at December 31, 2011, Land 299,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 17,650,000    
Gross Amounts at Which Carried at December 31, 2011, Total 17,949,000 [2]    
Accumulated Depreciation at December 31, 2011 10,252,000    
Year of Construction Jan. 01, 1965    
Date of Acquisition Jul. 01, 1969    
Net Rentable Square Feet 159,000 [3]    
Units 227    
Depreciation Life 35 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 17,949,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 10,252,000    
Park Adams [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 287,000 [1]    
Initial Cost, Buildings and Improvements 1,654,000 [1]    
Net Improvements (Retirement) since Acquisition 9,808,000    
Gross Amounts at Which Carried at December 31, 2011, Land 287,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 11,462,000    
Gross Amounts at Which Carried at December 31, 2011, Total 11,749,000 [2]    
Accumulated Depreciation at December 31, 2011 7,856,000    
Year of Construction Jan. 01, 1959    
Date of Acquisition Jan. 01, 1969    
Net Rentable Square Feet 173,000 [3]    
Units 200    
Depreciation Life 35 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 11,749,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 7,856,000    
Munson Hill Towers [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 322,000 [1]    
Initial Cost, Buildings and Improvements 3,337,000 [1]    
Net Improvements (Retirement) since Acquisition 15,359,000    
Gross Amounts at Which Carried at December 31, 2011, Land 322,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 18,696,000    
Gross Amounts at Which Carried at December 31, 2011, Total 19,018,000 [2]    
Accumulated Depreciation at December 31, 2011 13,331,000    
Year of Construction Jan. 01, 1963    
Date of Acquisition Jan. 01, 1970    
Net Rentable Square Feet 258,000 [3]    
Units 279    
Depreciation Life 33 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 19,018,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 13,331,000    
The Ashby at McLean [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 4,356,000 [1]    
Initial Cost, Buildings and Improvements 17,102,000 [1]    
Net Improvements (Retirement) since Acquisition 16,156,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,356,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 33,258,000    
Gross Amounts at Which Carried at December 31, 2011, Total 37,614,000 [2]    
Accumulated Depreciation at December 31, 2011 19,402,000    
Year of Construction Jan. 01, 1982    
Date of Acquisition Aug. 01, 1996    
Net Rentable Square Feet 274,000 [3]    
Units 256    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 37,614,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 19,402,000    
Walker House Apartments [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland [5]    
Initial Cost, Land 2,851,000 [1],[5]    
Initial Cost, Buildings and Improvements 7,946,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 6,827,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 2,851,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 14,773,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 17,624,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 9,101,000 [5]    
Year of Construction Jan. 01, 1971 [5]    
Date of Acquisition Mar. 01, 1996 [5]    
Net Rentable Square Feet 157,000 [3]    
Units 212    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 17,624,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 9,101,000 [5]    
Bethesda Hill Apartments [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland [5]    
Initial Cost, Land 3,900,000 [1],[5]    
Initial Cost, Buildings and Improvements 13,412,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 12,116,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 3,900,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 25,528,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 29,428,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 14,758,000 [5]    
Year of Construction Jan. 01, 1986 [5]    
Date of Acquisition Nov. 01, 1997 [5]    
Net Rentable Square Feet 225,000 [3],[5]    
Units 195    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 29,428,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 14,758,000 [5]    
Bennett Park [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 2,861,000 [1]    
Initial Cost, Buildings and Improvements 917,000 [1]    
Net Improvements (Retirement) since Acquisition 79,425,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,774,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 78,429,000    
Gross Amounts at Which Carried at December 31, 2011, Total 83,203,000 [2]    
Accumulated Depreciation at December 31, 2011 23,117,000    
Year of Construction Jan. 01, 2007    
Date of Acquisition Feb. 01, 2001    
Net Rentable Square Feet 214,000 [3]    
Units 224    
Depreciation Life 28 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 83,203,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 23,117,000    
The Clayborne [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 269,000 [1]    
Initial Cost, Buildings and Improvements 0 [1]    
Net Improvements (Retirement) since Acquisition 30,527,000    
Gross Amounts at Which Carried at December 31, 2011, Land 699,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 30,097,000    
Gross Amounts at Which Carried at December 31, 2011, Total 30,796,000 [2]    
Accumulated Depreciation at December 31, 2011 10,245,000    
Year of Construction Jan. 01, 2008    
Date of Acquisition Jun. 01, 2003    
Net Rentable Square Feet 60,000 [3]    
Units 74    
Depreciation Life 26 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 30,796,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 10,245,000    
The Kenmore [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC [5]    
Initial Cost, Land 28,222,000 [1],[5]    
Initial Cost, Buildings and Improvements 33,955,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 6,776,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 28,222,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 40,731,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 68,953,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 7,219,000 [5]    
Year of Construction Jan. 01, 1948 [5]    
Date of Acquisition Sep. 01, 2008 [5]    
Net Rentable Square Feet 268,000 [3]    
Units 374    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 68,953,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 7,219,000 [5]    
The Paramount [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 8,568,000 [1]    
Initial Cost, Buildings and Improvements 38,716,000 [1]    
Net Improvements (Retirement) since Acquisition 119,000    
Gross Amounts at Which Carried at December 31, 2011, Land 8,568,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 38,835,000    
Gross Amounts at Which Carried at December 31, 2011, Total 47,403,000 [2]    
Accumulated Depreciation at December 31, 2011 366,000    
Year of Construction Jan. 01, 1984    
Date of Acquisition Oct. 01, 2013 [5]    
Net Rentable Square Feet 141,000 [3]    
Units 135    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 47,403,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 366,000    
North Glebe, 650 and 1219 First Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Land Available for Development 48,100,000    
Six Fifty North Glebe Road [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia [7]    
Initial Cost, Land 12,787,000 [1],[7]    
Initial Cost, Buildings and Improvements 0 [1],[7]    
Net Improvements (Retirement) since Acquisition 14,556,000 [7]    
Gross Amounts at Which Carried at December 31, 2011, Land 27,343,000 [7]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 0 [7]    
Gross Amounts at Which Carried at December 31, 2011, Total 27,343,000 [2],[7]    
Accumulated Depreciation at December 31, 2011 0 [7]    
Date of Acquisition Jun. 01, 2011 [7]    
Net Rentable Square Feet 0    
Units 0    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 27,343,000 [2],[7]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 0 [7]    
1219 First Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia [7]    
Initial Cost, Land 14,046,000 [1],[7]    
Initial Cost, Buildings and Improvements 0 [1],[7]    
Net Improvements (Retirement) since Acquisition 6,742,000 [7]    
Gross Amounts at Which Carried at December 31, 2011, Land 20,788,000 [7]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 0 [7]    
Gross Amounts at Which Carried at December 31, 2011, Total 20,788,000 [2],[7]    
Accumulated Depreciation at December 31, 2011 0 [7]    
Date of Acquisition Nov. 01, 2011 [7]    
Net Rentable Square Feet 0    
Units 0    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 20,788,000 [2],[7]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 0 [7]    
Office Buildings [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Initial Cost, Land 263,723,000 [1]    
Initial Cost, Buildings and Improvements 812,034,000 [1]    
Net Improvements (Retirement) since Acquisition 233,379,000    
Gross Amounts at Which Carried at December 31, 2011, Land 252,852,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 1,056,284,000    
Gross Amounts at Which Carried at December 31, 2011, Total 1,309,136,000 [2]    
Accumulated Depreciation at December 31, 2011 336,608,000    
Net Rentable Square Feet 4,557,000 [3]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 1,309,136,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 336,608,000    
1901 Pennsylvania Avenue [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 892,000 [1]    
Initial Cost, Buildings and Improvements 3,481,000 [1]    
Net Improvements (Retirement) since Acquisition 15,955,000    
Gross Amounts at Which Carried at December 31, 2011, Land 892,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 19,436,000    
Gross Amounts at Which Carried at December 31, 2011, Total 20,328,000 [2]    
Accumulated Depreciation at December 31, 2011 14,068,000    
Year of Construction Jan. 01, 1960    
Date of Acquisition May 01, 1977    
Net Rentable Square Feet 101,000    
Depreciation Life 28 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 20,328,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 14,068,000    
51 Monroe Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 840,000 [1]    
Initial Cost, Buildings and Improvements 10,869,000 [1]    
Net Improvements (Retirement) since Acquisition 26,553,000    
Gross Amounts at Which Carried at December 31, 2011, Land 840,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 37,422,000    
Gross Amounts at Which Carried at December 31, 2011, Total 38,262,000 [2]    
Accumulated Depreciation at December 31, 2011 26,144,000    
Year of Construction Jan. 01, 1975    
Date of Acquisition Aug. 01, 1979    
Net Rentable Square Feet 222,000    
Depreciation Life 41 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 38,262,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 26,144,000    
515 King Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 4,102,000 [1]    
Initial Cost, Buildings and Improvements 3,931,000 [1]    
Net Improvements (Retirement) since Acquisition 5,494,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,102,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 9,425,000    
Gross Amounts at Which Carried at December 31, 2011, Total 13,527,000 [2]    
Accumulated Depreciation at December 31, 2011 4,989,000    
Year of Construction Jan. 01, 1966    
Date of Acquisition Jul. 01, 1992    
Net Rentable Square Feet 75,000    
Depreciation Life 50 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 13,527,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 4,989,000    
6110 Executive Boulevard [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 4,621,000 [1]    
Initial Cost, Buildings and Improvements 11,926,000 [1]    
Net Improvements (Retirement) since Acquisition 15,144,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,621,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 27,070,000    
Gross Amounts at Which Carried at December 31, 2011, Total 31,691,000 [2]    
Accumulated Depreciation at December 31, 2011 16,490,000    
Year of Construction Jan. 01, 1971    
Date of Acquisition Jan. 01, 1995    
Net Rentable Square Feet 203,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 31,691,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 16,490,000    
1220 19th Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 7,803,000 [1]    
Initial Cost, Buildings and Improvements 11,366,000 [1]    
Net Improvements (Retirement) since Acquisition 10,612,000    
Gross Amounts at Which Carried at December 31, 2011, Land 7,803,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 21,978,000    
Gross Amounts at Which Carried at December 31, 2011, Total 29,781,000 [2]    
Accumulated Depreciation at December 31, 2011 11,233,000    
Year of Construction Jan. 01, 1976    
Date of Acquisition Nov. 01, 1995    
Net Rentable Square Feet 104,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 29,781,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 11,233,000    
1600 Wilson Boulevard [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 6,661,000 [1]    
Initial Cost, Buildings and Improvements 16,742,000 [1]    
Net Improvements (Retirement) since Acquisition 20,384,000    
Gross Amounts at Which Carried at December 31, 2011, Land 6,661,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 37,126,000    
Gross Amounts at Which Carried at December 31, 2011, Total 43,787,000 [2]    
Accumulated Depreciation at December 31, 2011 16,668,000    
Year of Construction Jan. 01, 1973    
Date of Acquisition Oct. 01, 1997    
Net Rentable Square Feet 168,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 43,787,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 16,668,000    
7900 Westpark Drive [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia [8]    
Initial Cost, Land 12,049,000 [1],[8]    
Initial Cost, Buildings and Improvements 71,825,000 [1]    
Net Improvements (Retirement) since Acquisition 40,805,000 [8]    
Gross Amounts at Which Carried at December 31, 2011, Land 12,049,000 [8]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 112,630,000 [8]    
Gross Amounts at Which Carried at December 31, 2011, Total 124,679,000 [2],[8]    
Accumulated Depreciation at December 31, 2011 60,969,000 [8]    
Year of Construction Jan. 01, 1972    
Date of Acquisition Nov. 01, 1997    
Net Rentable Square Feet 530,000    
Depreciation Life 30 years [6]    
Development in Process 3,300,000    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 124,679,000 [2],[8]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 60,969,000 [8]    
600 Jefferson Plaza [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 2,296,000 [1]    
Initial Cost, Buildings and Improvements 12,188,000 [1]    
Net Improvements (Retirement) since Acquisition 6,199,000    
Gross Amounts at Which Carried at December 31, 2011, Land 2,296,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 18,387,000    
Gross Amounts at Which Carried at December 31, 2011, Total 20,683,000 [2]    
Accumulated Depreciation at December 31, 2011 8,988,000    
Year of Construction Jan. 01, 1985    
Date of Acquisition May 01, 1999    
Net Rentable Square Feet 113,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 20,683,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 8,988,000    
Wayne Plaza [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 1,564,000 [1]    
Initial Cost, Buildings and Improvements 6,243,000 [1]    
Net Improvements (Retirement) since Acquisition 8,431,000    
Gross Amounts at Which Carried at December 31, 2011, Land 1,564,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 14,674,000    
Gross Amounts at Which Carried at December 31, 2011, Total 16,238,000 [2]    
Accumulated Depreciation at December 31, 2011 7,281,000    
Year of Construction Jan. 01, 1970    
Date of Acquisition May 01, 2000    
Net Rentable Square Feet 96,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 16,238,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 7,281,000    
Courthouse Square [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 0 [1]    
Initial Cost, Buildings and Improvements 17,096,000 [1]    
Net Improvements (Retirement) since Acquisition 7,441,000    
Gross Amounts at Which Carried at December 31, 2011, Land 0    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 24,537,000    
Gross Amounts at Which Carried at December 31, 2011, Total 24,537,000 [2]    
Accumulated Depreciation at December 31, 2011 10,899,000    
Year of Construction Jan. 01, 1979    
Date of Acquisition Oct. 01, 2000    
Net Rentable Square Feet 115,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 24,537,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 10,899,000    
One Central Plaza [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 5,480,000 [1]    
Initial Cost, Buildings and Improvements 39,107,000 [1]    
Net Improvements (Retirement) since Acquisition 16,750,000    
Gross Amounts at Which Carried at December 31, 2011, Land 5,480,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 55,857,000    
Gross Amounts at Which Carried at December 31, 2011, Total 61,337,000 [2]    
Accumulated Depreciation at December 31, 2011 26,059,000    
Year of Construction Jan. 01, 1974    
Date of Acquisition Apr. 01, 2001    
Net Rentable Square Feet 267,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 61,337,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 26,059,000    
1776 G Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 31,500,000 [1]    
Initial Cost, Buildings and Improvements 54,327,000 [1]    
Net Improvements (Retirement) since Acquisition 4,865,000    
Gross Amounts at Which Carried at December 31, 2011, Land 31,500,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 59,192,000    
Gross Amounts at Which Carried at December 31, 2011, Total 90,692,000 [2]    
Accumulated Depreciation at December 31, 2011 23,247,000    
Year of Construction Jan. 01, 1979    
Date of Acquisition Aug. 01, 2003    
Net Rentable Square Feet 263,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 90,692,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 23,247,000    
Dulles Station II [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia [8]    
Initial Cost, Land 15,001,000 [1],[8]    
Initial Cost, Buildings and Improvements 494,000 [1],[8]    
Net Improvements (Retirement) since Acquisition (3,425,000) [8]    
Gross Amounts at Which Carried at December 31, 2011, Land 4,130,000 [8]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 7,940,000 [8]    
Gross Amounts at Which Carried at December 31, 2011, Total 12,070,000 [2],[8]    
Accumulated Depreciation at December 31, 2011 291,000 [8]    
Date of Acquisition Dec. 01, 2005 [8]    
Net Rentable Square Feet 0    
Area of land 360,000    
Land Placed In Service 500,000    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 12,070,000 [2],[8]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 291,000 [8]    
West Gude Drive [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 11,580,000 [1]    
Initial Cost, Buildings and Improvements 43,240,000 [1]    
Net Improvements (Retirement) since Acquisition 10,876,000    
Gross Amounts at Which Carried at December 31, 2011, Land 11,580,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 54,116,000    
Gross Amounts at Which Carried at December 31, 2011, Total 65,696,000 [2]    
Accumulated Depreciation at December 31, 2011 15,195,000    
Year of Construction Jan. 01, 1984    
Date of Acquisition Aug. 01, 2006    
Net Rentable Square Feet 277,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 65,696,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 15,195,000    
Monument II [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 10,244,000 [1]    
Initial Cost, Buildings and Improvements 65,205,000 [1]    
Net Improvements (Retirement) since Acquisition 4,733,000    
Gross Amounts at Which Carried at December 31, 2011, Land 10,244,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 69,938,000    
Gross Amounts at Which Carried at December 31, 2011, Total 80,182,000 [2]    
Accumulated Depreciation at December 31, 2011 17,810,000    
Year of Construction Jan. 01, 2000    
Date of Acquisition Mar. 01, 2007    
Net Rentable Square Feet 207,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 80,182,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 17,810,000    
2000 M Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 0 [1]    
Initial Cost, Buildings and Improvements 61,101,000 [1]    
Net Improvements (Retirement) since Acquisition 20,866,000    
Gross Amounts at Which Carried at December 31, 2011, Land 0    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 81,967,000    
Gross Amounts at Which Carried at December 31, 2011, Total 81,967,000 [2]    
Accumulated Depreciation at December 31, 2011 17,061,000    
Year of Construction Jan. 01, 1971    
Date of Acquisition Dec. 01, 2007    
Net Rentable Square Feet 230,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 81,967,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 17,061,000    
M Street 2445 [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC [5]    
Initial Cost, Land 46,887,000 [1],[5]    
Initial Cost, Buildings and Improvements 106,743,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 3,060,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 46,887,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 109,803,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 156,690,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 22,179,000 [5]    
Year of Construction Jan. 01, 1986    
Date of Acquisition Dec. 01, 2008    
Net Rentable Square Feet 290,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 156,690,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 22,179,000 [5]    
Quantico Building E [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 4,518,000 [1]    
Initial Cost, Buildings and Improvements 24,801,000 [1]    
Net Improvements (Retirement) since Acquisition 428,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,518,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 25,229,000    
Gross Amounts at Which Carried at December 31, 2011, Total 29,747,000 [2]    
Accumulated Depreciation at December 31, 2011 5,100,000    
Year of Construction Jan. 01, 2007    
Date of Acquisition Jun. 01, 2010    
Net Rentable Square Feet 134,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 29,747,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 5,100,000    
Quantico Building G [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 4,897,000 [1]    
Initial Cost, Buildings and Improvements 25,376,000 [1]    
Net Improvements (Retirement) since Acquisition (129,000)    
Gross Amounts at Which Carried at December 31, 2011, Land 4,897,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 25,247,000    
Gross Amounts at Which Carried at December 31, 2011, Total 30,144,000 [2]    
Accumulated Depreciation at December 31, 2011 5,217,000    
Year of Construction Jan. 01, 2009    
Date of Acquisition Jun. 01, 2010    
Net Rentable Square Feet 136,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 30,144,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 5,217,000    
1140 Connecticut Avenue [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 25,226,000 [1]    
Initial Cost, Buildings and Improvements 50,495,000 [1]    
Net Improvements (Retirement) since Acquisition 8,124,000    
Gross Amounts at Which Carried at December 31, 2011, Land 25,226,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 58,619,000    
Gross Amounts at Which Carried at December 31, 2011, Total 83,845,000 [2]    
Accumulated Depreciation at December 31, 2011 7,425,000    
Year of Construction Jan. 01, 1966    
Date of Acquisition Jan. 01, 2011    
Net Rentable Square Feet 184,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 83,845,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 7,425,000    
1227 25th Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 17,505,000 [1]    
Initial Cost, Buildings and Improvements 21,319,000 [1]    
Net Improvements (Retirement) since Acquisition 2,339,000    
Gross Amounts at Which Carried at December 31, 2011, Land 17,505,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 23,658,000    
Gross Amounts at Which Carried at December 31, 2011, Total 41,163,000 [2]    
Accumulated Depreciation at December 31, 2011 3,158,000    
Year of Construction Jan. 01, 1988    
Date of Acquisition Mar. 01, 2011    
Net Rentable Square Feet 132,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 41,163,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 3,158,000    
Braddock Place Member
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 18,817,000 [1]    
Initial Cost, Buildings and Improvements 71,250,000 [1]    
Net Improvements (Retirement) since Acquisition 5,564,000    
Gross Amounts at Which Carried at December 31, 2011, Land 18,817,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 76,814,000    
Gross Amounts at Which Carried at December 31, 2011, Total 95,631,000 [2]    
Accumulated Depreciation at December 31, 2011 8,542,000    
Year of Construction Jan. 01, 1985    
Date of Acquisition Sep. 01, 2011    
Net Rentable Square Feet 345,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 95,631,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 8,542,000    
John Marshall II Member
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia [5]    
Initial Cost, Land 13,490,000 [1],[5]    
Initial Cost, Buildings and Improvements 53,024,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 173,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 13,490,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 53,197,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 66,687,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 5,071,000 [5]    
Year of Construction Jan. 01, 1996    
Date of Acquisition Sep. 01, 2011    
Net Rentable Square Feet 223,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 66,687,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 5,071,000 [5]    
Fairgate at Ballston [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 17,750,000 [1]    
Initial Cost, Buildings and Improvements 29,885,000 [1]    
Net Improvements (Retirement) since Acquisition 2,137,000    
Gross Amounts at Which Carried at December 31, 2011, Land 17,750,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 32,022,000    
Gross Amounts at Which Carried at December 31, 2011, Total 49,772,000 [2]    
Accumulated Depreciation at December 31, 2011 2,524,000    
Year of Construction Jan. 01, 1988    
Date of Acquisition Jun. 01, 2012    
Net Rentable Square Feet 142,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 49,772,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 2,524,000    
Medical Office [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Initial Cost, Land 11,683,000 [1]    
Initial Cost, Buildings and Improvements 101,881,000 [1]    
Net Improvements (Retirement) since Acquisition 12,403,000    
Gross Amounts at Which Carried at December 31, 2011, Land 11,683,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 114,284,000    
Gross Amounts at Which Carried at December 31, 2011, Total 125,967,000 [2]    
Accumulated Depreciation at December 31, 2011 46,066,000    
Net Rentable Square Feet 427,000    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 125,967,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 46,066,000    
Woodburn Medical Park I [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 2,563,000 [1]    
Initial Cost, Buildings and Improvements 12,460,000 [1]    
Net Improvements (Retirement) since Acquisition 4,393,000    
Gross Amounts at Which Carried at December 31, 2011, Land 2,563,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 16,853,000    
Gross Amounts at Which Carried at December 31, 2011, Total 19,416,000 [2]    
Accumulated Depreciation at December 31, 2011 8,620,000    
Year of Construction Jan. 01, 1984    
Date of Acquisition Nov. 01, 1998    
Net Rentable Square Feet 77,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 19,416,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 8,620,000    
Woodburn Medical Park II [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 2,632,000 [1]    
Initial Cost, Buildings and Improvements 17,574,000 [1]    
Net Improvements (Retirement) since Acquisition 4,366,000    
Gross Amounts at Which Carried at December 31, 2011, Land 2,632,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 21,940,000    
Gross Amounts at Which Carried at December 31, 2011, Total 24,572,000 [2]    
Accumulated Depreciation at December 31, 2011 10,901,000    
Year of Construction Jan. 01, 1988    
Date of Acquisition Nov. 01, 1998    
Net Rentable Square Feet 97,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 24,572,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 10,901,000    
8501 Arlington Boulevard [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 2,071,000 [1]    
Initial Cost, Buildings and Improvements 26,317,000 [1]    
Net Improvements (Retirement) since Acquisition 1,335,000    
Gross Amounts at Which Carried at December 31, 2011, Land 2,071,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 27,652,000    
Gross Amounts at Which Carried at December 31, 2011, Total 29,723,000 [2]    
Accumulated Depreciation at December 31, 2011 9,733,000    
Year of Construction Jan. 01, 2000    
Date of Acquisition Oct. 01, 2003    
Net Rentable Square Feet 91,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 29,723,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 9,733,000    
8503 Arlington Boulevard [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 1,598,000 [1]    
Initial Cost, Buildings and Improvements 25,850,000 [1]    
Net Improvements (Retirement) since Acquisition 1,521,000    
Gross Amounts at Which Carried at December 31, 2011, Land 1,598,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 27,371,000    
Gross Amounts at Which Carried at December 31, 2011, Total 28,969,000 [2]    
Accumulated Depreciation at December 31, 2011 9,474,000    
Year of Construction Jan. 01, 2001    
Date of Acquisition Oct. 01, 2003    
Net Rentable Square Feet 87,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 28,969,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 9,474,000    
8505 Arlington Boulevard [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 2,819,000 [1]    
Initial Cost, Buildings and Improvements 19,680,000 [1]    
Net Improvements (Retirement) since Acquisition 788,000    
Gross Amounts at Which Carried at December 31, 2011, Land 2,819,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 20,468,000    
Gross Amounts at Which Carried at December 31, 2011, Total 23,287,000 [2]    
Accumulated Depreciation at December 31, 2011 7,338,000    
Year of Construction Jan. 01, 2002    
Date of Acquisition Oct. 01, 2003    
Net Rentable Square Feet 75,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 23,287,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 7,338,000    
Retail Centers [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Initial Cost, Land 121,758,000 [1]    
Initial Cost, Buildings and Improvements 226,365,000 [1]    
Net Improvements (Retirement) since Acquisition 68,275,000    
Gross Amounts at Which Carried at December 31, 2011, Land 122,336,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 294,062,000    
Gross Amounts at Which Carried at December 31, 2011, Total 416,398,000 [2]    
Accumulated Depreciation at December 31, 2011 96,463,000    
Net Rentable Square Feet 2,449,000    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 416,398,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 96,463,000    
Takoma Park [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 415,000 [1]    
Initial Cost, Buildings and Improvements 1,084,000 [1]    
Net Improvements (Retirement) since Acquisition 238,000    
Gross Amounts at Which Carried at December 31, 2011, Land 415,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 1,322,000    
Gross Amounts at Which Carried at December 31, 2011, Total 1,737,000 [2]    
Accumulated Depreciation at December 31, 2011 1,184,000    
Year of Construction Jan. 01, 1962    
Date of Acquisition Jul. 01, 1963    
Net Rentable Square Feet 51,000    
Depreciation Life 50 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 1,737,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 1,184,000    
Westminster [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 519,000 [1]    
Initial Cost, Buildings and Improvements 1,775,000 [1]    
Net Improvements (Retirement) since Acquisition 9,171,000    
Gross Amounts at Which Carried at December 31, 2011, Land 519,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 10,946,000    
Gross Amounts at Which Carried at December 31, 2011, Total 11,465,000 [2]    
Accumulated Depreciation at December 31, 2011 6,534,000    
Year of Construction Jan. 01, 1969    
Date of Acquisition Sep. 01, 1972    
Net Rentable Square Feet 150,000    
Depreciation Life 37 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 11,465,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 6,534,000    
Concord Centre [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 413,000 [1]    
Initial Cost, Buildings and Improvements 850,000 [1]    
Net Improvements (Retirement) since Acquisition 3,511,000    
Gross Amounts at Which Carried at December 31, 2011, Land 413,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 4,361,000    
Gross Amounts at Which Carried at December 31, 2011, Total 4,774,000 [2]    
Accumulated Depreciation at December 31, 2011 2,966,000    
Year of Construction Jan. 01, 1960    
Date of Acquisition Dec. 01, 1973    
Net Rentable Square Feet 76,000    
Depreciation Life 33 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 4,774,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 2,966,000    
Wheaton Park [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 796,000 [1]    
Initial Cost, Buildings and Improvements 857,000 [1]    
Net Improvements (Retirement) since Acquisition 4,455,000    
Gross Amounts at Which Carried at December 31, 2011, Land 796,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 5,312,000    
Gross Amounts at Which Carried at December 31, 2011, Total 6,108,000 [2]    
Accumulated Depreciation at December 31, 2011 3,364,000    
Year of Construction Jan. 01, 1967    
Date of Acquisition Sep. 01, 1977    
Net Rentable Square Feet 74,000    
Depreciation Life 50 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 6,108,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 3,364,000    
Bradlee [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 4,152,000 [1]    
Initial Cost, Buildings and Improvements 5,383,000 [1]    
Net Improvements (Retirement) since Acquisition 8,261,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,152,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 13,644,000    
Gross Amounts at Which Carried at December 31, 2011, Total 17,796,000 [2]    
Accumulated Depreciation at December 31, 2011 9,639,000    
Year of Construction Jan. 01, 1955    
Date of Acquisition Dec. 01, 1984    
Net Rentable Square Feet 168,000    
Depreciation Life 40 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 17,796,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 9,639,000    
Chevy Chase Metro Plaza [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Washington, DC    
Initial Cost, Land 1,549,000 [1]    
Initial Cost, Buildings and Improvements 4,304,000 [1]    
Net Improvements (Retirement) since Acquisition 5,366,000    
Gross Amounts at Which Carried at December 31, 2011, Land 1,549,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 9,670,000    
Gross Amounts at Which Carried at December 31, 2011, Total 11,219,000 [2]    
Accumulated Depreciation at December 31, 2011 6,012,000    
Year of Construction Jan. 01, 1975    
Date of Acquisition Sep. 01, 1985    
Net Rentable Square Feet 49,000    
Depreciation Life 50 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 11,219,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 6,012,000    
Montgomery Village Center [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 11,625,000 [1]    
Initial Cost, Buildings and Improvements 9,105,000 [1]    
Net Improvements (Retirement) since Acquisition 3,252,000    
Gross Amounts at Which Carried at December 31, 2011, Land 11,625,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 12,357,000    
Gross Amounts at Which Carried at December 31, 2011, Total 23,982,000 [2]    
Accumulated Depreciation at December 31, 2011 5,502,000    
Year of Construction Jan. 01, 1969    
Date of Acquisition Dec. 01, 1992    
Net Rentable Square Feet 197,000    
Depreciation Life 50 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 23,982,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 5,502,000    
Shoppes of Foxchase [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 5,838,000 [1]    
Initial Cost, Buildings and Improvements 2,979,000 [1]    
Net Improvements (Retirement) since Acquisition 13,245,000    
Gross Amounts at Which Carried at December 31, 2011, Land 5,838,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 16,224,000    
Gross Amounts at Which Carried at December 31, 2011, Total 22,062,000 [2]    
Accumulated Depreciation at December 31, 2011 5,419,000    
Year of Construction Jan. 01, 1960    
Date of Acquisition Jun. 01, 1994    
Net Rentable Square Feet 134,000    
Depreciation Life 50 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 22,062,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 5,419,000    
Frederick County Square [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 6,561,000 [1]    
Initial Cost, Buildings and Improvements 6,830,000 [1]    
Net Improvements (Retirement) since Acquisition 4,105,000    
Gross Amounts at Which Carried at December 31, 2011, Land 6,561,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 10,935,000    
Gross Amounts at Which Carried at December 31, 2011, Total 17,496,000 [2]    
Accumulated Depreciation at December 31, 2011 6,381,000    
Year of Construction Jan. 01, 1973    
Date of Acquisition Aug. 01, 1995    
Net Rentable Square Feet 227,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 17,496,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 6,381,000    
800 S. Washington Street [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Virginia    
Initial Cost, Land 2,904,000 [1]    
Initial Cost, Buildings and Improvements 5,489,000 [1]    
Net Improvements (Retirement) since Acquisition 5,999,000    
Gross Amounts at Which Carried at December 31, 2011, Land 2,904,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 11,488,000    
Gross Amounts at Which Carried at December 31, 2011, Total 14,392,000 [2]    
Accumulated Depreciation at December 31, 2011 4,106,000    
Year of Construction Jan. 01, 1951    
Date of Acquisition Jun. 01, 1998    
Net Rentable Square Feet 47,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 14,392,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 4,106,000    
Centre at Hagerstown . [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 13,029,000 [1]    
Initial Cost, Buildings and Improvements 25,415,000 [1]    
Net Improvements (Retirement) since Acquisition 2,306,000    
Gross Amounts at Which Carried at December 31, 2011, Land 13,029,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 27,721,000    
Gross Amounts at Which Carried at December 31, 2011, Total 40,750,000 [2]    
Accumulated Depreciation at December 31, 2011 10,836,000    
Year of Construction Jan. 01, 2000    
Date of Acquisition Jun. 01, 2002    
Net Rentable Square Feet 332,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 40,750,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 10,836,000    
Frederick Crossing [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 12,759,000 [1]    
Initial Cost, Buildings and Improvements 35,477,000 [1]    
Net Improvements (Retirement) since Acquisition 2,206,000    
Gross Amounts at Which Carried at December 31, 2011, Land 12,759,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 37,683,000    
Gross Amounts at Which Carried at December 31, 2011, Total 50,442,000 [2]    
Accumulated Depreciation at December 31, 2011 11,701,000    
Year of Construction Jan. 01, 1999    
Date of Acquisition Mar. 01, 2005    
Net Rentable Square Feet 295,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 50,442,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 11,701,000    
Randolph Shopping Center [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 4,928,000 [1]    
Initial Cost, Buildings and Improvements 13,025,000 [1]    
Net Improvements (Retirement) since Acquisition 727,000    
Gross Amounts at Which Carried at December 31, 2011, Land 4,928,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 13,752,000    
Gross Amounts at Which Carried at December 31, 2011, Total 18,680,000 [2]    
Accumulated Depreciation at December 31, 2011 3,848,000    
Year of Construction Jan. 01, 1972    
Date of Acquisition May 01, 2006    
Net Rentable Square Feet 82,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 18,680,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 3,848,000    
Montrose Shopping Center [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 11,612,000 [1]    
Initial Cost, Buildings and Improvements 22,410,000 [1]    
Net Improvements (Retirement) since Acquisition 2,545,000    
Gross Amounts at Which Carried at December 31, 2011, Land 11,612,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 24,955,000    
Gross Amounts at Which Carried at December 31, 2011, Total 36,567,000 [2]    
Accumulated Depreciation at December 31, 2011 6,934,000    
Year of Construction Jan. 01, 1970    
Date of Acquisition May 01, 2006    
Net Rentable Square Feet 145,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 36,567,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 6,934,000    
Gateway Overlook [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland    
Initial Cost, Land 28,816,000 [1]    
Initial Cost, Buildings and Improvements 52,249,000 [1]    
Net Improvements (Retirement) since Acquisition 1,240,000    
Gross Amounts at Which Carried at December 31, 2011, Land 29,394,000    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 52,911,000    
Gross Amounts at Which Carried at December 31, 2011, Total 82,305,000 [2]    
Accumulated Depreciation at December 31, 2011 8,328,000    
Year of Construction Jan. 01, 2007    
Date of Acquisition Dec. 01, 2010    
Net Rentable Square Feet 223,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 82,305,000 [2]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 8,328,000    
Olney Village Center Member
     
Real Estate and Accumulated Depreciation [Line Items]      
Location Maryland [5]    
Initial Cost, Land 15,842,000 [1],[5]    
Initial Cost, Buildings and Improvements 39,133,000 [1],[5]    
Net Improvements (Retirement) since Acquisition 1,648,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Land 15,842,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements 40,781,000 [5]    
Gross Amounts at Which Carried at December 31, 2011, Total 56,623,000 [2],[5]    
Accumulated Depreciation at December 31, 2011 3,709,000 [5]    
Year of Construction Jan. 01, 1979 [5]    
Date of Acquisition Aug. 01, 2011 [5]    
Net Rentable Square Feet 199,000    
Depreciation Life 30 years [6]    
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]      
Balance, end of period 56,623,000 [2],[5]    
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]      
Balance, end of period 3,709,000 [5]    
650 N Glebe [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Mortgage notes payable 7,297,000 0 [10],[9]  
3801 Connecticut [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Secured Debt 35,400,000    
Kenmore Apartments [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Mortgage notes payable 34,937,000 35,535,000  
Walker House Apartments [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Secured Debt 16,500,000    
Olney Village Center Member
     
Real Estate and Accumulated Depreciation [Line Items]      
Mortgage notes payable 20,743,000 22,343,000  
Bethesda Hill Apartments [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Secured Debt 29,100,000    
John Marshall II Member
     
Real Estate and Accumulated Depreciation [Line Items]      
Mortgage notes payable 52,563,000 53,274,000  
M Street 2445 [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Mortgage notes payable $ 98,102,000 [10] $ 96,848,000 [10]  
Minimum [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Useful Life 3 years    
Maximum [Member]
     
Real Estate and Accumulated Depreciation [Line Items]      
Useful Life 50 years    
[1] The purchase cost of real estate investments has been divided between land and buildings and improvements on the basis of management’s determination of the fair values.
[2] At December 31, 2013, total land, buildings and improvements are carried at $1,939.3 million for federal income tax purposes.
[3] Residential properties are presented in gross square feet.
[4] Includes non-cash accruals for capital items and assumed mortgages.
[5] At December 31, 2013, our properties were encumbered by non-recourse mortgage amounts as follows: $35.4 million on 3801 Connecticut Avenue, $16.5 million on Walker House, $29.1 million on Bethesda Hill, $34.9 million on The Kenmore, $98.1 million on 2445 M Street, $52.6 million on John Marshall II, and $20.7 million on Olney Village Center.
[6] The useful life shown is for the main structure. Buildings and improvements are depreciated over various useful lives ranging from 3 to 50 years.
[7] As of December 31, 2013, WRIT had under development via joint venture arrangements, a mid-rise multifamily property in Arlington, Virginia (650 North Glebe) and a high-rise multifamily property in Alexandria, Virginia (1225 First Street). The value not yet placed into service of these development projects via joint venture arrangements at December 31, 2013 was $48.1 million. 650 North Glebe was encumbered by a construction loan with a $7.3 million balance at December 31, 2013.
[8] As of December 31, 2013, WRIT had under development an office project with 360,000 square feet of office space and a parking garage to be developed in Herndon, VA (Dulles Station, Phase II). The total land value not yet placed in service of the development project at December 31, 2013 was $3.6 million. $0.5 million of Dulles Station, Phase II land was placed into service upon the completion of a portion of the parking garage structure. Additionally, WRIT had investments in various smaller development or redevelopment projects, including 7900 Westpark Drive. The total value of this redevelopment not yet placed in service is $3.3 million at December 31, 2013.
[9] Interest rate on 650 North Glebe Road is variable, based on LIBOR plus 2.15%. The maturity date can be extended for up to two years, subject to fees and compliance with certain provisions in the loan agreement, until February 20, 2018.
[10] Interest only is payable monthly until the maturity date upon which all unpaid principal and interest are payable in full.