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.