Schedule III (Details)

v2.4.0.6

Schedule III (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 units sqft		Dec. 31, 2011 sqft		Dec. 31, 2010 sqft
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost, Land	$ 528,576,000	[1]
Initial Cost, Buildings and Improvements	1,483,293,000	[1]
Net Improvements (Retirement) since Acquisition	517,264,000
Gross Amounts at Which Carried at December 31, 2011, Land	529,291,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	1,999,840,000
Gross Amounts at Which Carried at December 31, 2011, Total	2,529,131,000	[2]
Accumulated Depreciation at December 31, 2011	610,536,000
Net Rentable Square Feet	10,725,000	[3]
Units	2,540
Secured Debt	342,970,000		423,291,000
Mortgage notes payable	342,970,000		427,710,000
Real estate, federal income tax basis	2,148,544,000
Area of land	213,000		3,272,000		638,000
Land Available for Development	7,500,000
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance, beginning of period	2,449,872,000		2,443,127,000		2,341,461,000
Property acquisitions	47,772,000	[4]	352,658,000	[4]	140,584,000	[4]
Improvements	59,664,000	[4]	36,386,000	[4]	28,196,000	[4]
Impairment write-down	(2,097,000)		(16,416,000)		0
Write-off of disposed assets	(1,450,000)		(1,648,000)		(866,000)
Property sales	(24,630,000)		(364,235,000)		(66,248,000)
Balance, end of period	2,529,131,000		2,449,872,000		2,443,127,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance, beginning of period	535,732,000		538,786,000		475,245,000
Depreciation	84,949,000		84,167,000		83,302,000
Impairment write-down	0		(1,291,000)		0
Write-off of disposed assets	(1,124,000)		(1,648,000)		(866,000)
Property sales	(9,021,000)		(84,282,000)		(18,895,000)
Balance, end of period	610,536,000		535,732,000		538,786,000
Multifamily Properties [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost, Land	70,956,000	[1]
Initial Cost, Buildings and Improvements	85,559,000	[1]
Net Improvements (Retirement) since Acquisition	211,147,000
Gross Amounts at Which Carried at December 31, 2011, Land	81,918,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	285,743,000
Gross Amounts at Which Carried at December 31, 2011, Total	367,661,000	[2]
Accumulated Depreciation at December 31, 2011	120,036,000
Net Rentable Square Feet	2,137,000	[3]
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	9,023,000	[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	11,702,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	12,122,000	[2],[5]
Accumulated Depreciation at December 31, 2011	8,504,000	[5]
Year of Construction	Jan. 01, 1951	[5]
Date of Acquisition	Jan. 01, 1963	[5]
Net Rentable Square Feet	179,000	[3],[5]
Units	308	[5]
Depreciation Life	30 years	[5],[6]
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	9,881,000
Gross Amounts at Which Carried at December 31, 2011, Land	336,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	11,877,000
Gross Amounts at Which Carried at December 31, 2011, Total	12,213,000	[2]
Accumulated Depreciation at December 31, 2011	7,180,000
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]
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	14,461,000
Gross Amounts at Which Carried at December 31, 2011, Land	299,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	17,023,000
Gross Amounts at Which Carried at December 31, 2011, Total	17,322,000	[2]
Accumulated Depreciation at December 31, 2011	9,472,000
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]
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	9,141,000
Gross Amounts at Which Carried at December 31, 2011, Land	287,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	10,795,000
Gross Amounts at Which Carried at December 31, 2011, Total	11,082,000	[2]
Accumulated Depreciation at December 31, 2011	7,386,000
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]
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	14,847,000
Gross Amounts at Which Carried at December 31, 2011, Land	322,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	18,183,000
Gross Amounts at Which Carried at December 31, 2011, Total	18,505,000	[2]
Accumulated Depreciation at December 31, 2011	12,589,000
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]
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	15,148,000
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	32,250,000
Gross Amounts at Which Carried at December 31, 2011, Total	36,606,000	[2]
Accumulated Depreciation at December 31, 2011	17,975,000
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]
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	6,688,000	[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	14,634,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	17,485,000	[2],[5]
Accumulated Depreciation at December 31, 2011	8,508,000	[5]
Year of Construction	Jan. 01, 1971	[5]
Date of Acquisition	Mar. 01, 1996	[5]
Net Rentable Square Feet	157,000	[3],[5]
Units	212	[5]
Depreciation Life	30 years	[5],[6]
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	11,903,000	[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	25,315,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	29,215,000	[2],[5]
Accumulated Depreciation at December 31, 2011	13,593,000	[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	[5]
Depreciation Life	30 years	[5],[6]
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	78,855,000
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	77,859,000
Gross Amounts at Which Carried at December 31, 2011, Total	82,633,000	[2]
Accumulated Depreciation at December 31, 2011	20,017,000
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]
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	30,451,000
Gross Amounts at Which Carried at December 31, 2011, Land	699,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	30,020,000
Gross Amounts at Which Carried at December 31, 2011, Total	30,719,000	[2]
Accumulated Depreciation at December 31, 2011	8,994,000
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]
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	2,130,000	[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	36,085,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	64,307,000	[2],[5]
Accumulated Depreciation at December 31, 2011	5,818,000	[5]
Year of Construction	Jan. 01, 1948	[5]
Date of Acquisition	Sep. 01, 2008	[5]
Net Rentable Square Feet	268,000	[3],[5]
Units	374	[5]
Depreciation Life	30 years	[5],[6]
North Glebe, 650 and 1219 First Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Land Available for Development	35,500,000
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	2,858,000	[7]
Gross Amounts at Which Carried at December 31, 2011, Land	15,645,000	[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	15,645,000	[2],[7]
Accumulated Depreciation at December 31, 2011	0	[7]
Date of Acquisition	Jun. 01, 2011	[7]
Net Rentable Square Feet	0	[3],[7]
Units	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	5,761,000	[7]
Gross Amounts at Which Carried at December 31, 2011, Land	19,807,000	[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	19,807,000	[2],[7]
Accumulated Depreciation at December 31, 2011	0	[7]
Date of Acquisition	Nov. 01, 2011	[7]
Net Rentable Square Feet	0	[3],[7]
Units	0	[5],[7]
Office Buildings [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost, Land	274,683,000	[1]
Initial Cost, Buildings and Improvements	863,221,000	[1]
Net Improvements (Retirement) since Acquisition	204,157,000
Gross Amounts at Which Carried at December 31, 2011, Land	263,812,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	1,078,249,000
Gross Amounts at Which Carried at December 31, 2011, Total	1,342,061,000	[2]
Accumulated Depreciation at December 31, 2011	309,483,000
Net Rentable Square Feet	4,855,000	[3]
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	15,100,000
Gross Amounts at Which Carried at December 31, 2011, Land	892,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	18,581,000
Gross Amounts at Which Carried at December 31, 2011, Total	19,473,000	[2]
Accumulated Depreciation at December 31, 2011	13,478,000
Year of Construction	Jan. 01, 1960
Date of Acquisition	May 01, 1977
Net Rentable Square Feet	99,000
Depreciation Life	28 years	[6]
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	24,173,000
Gross Amounts at Which Carried at December 31, 2011, Land	840,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	35,042,000
Gross Amounts at Which Carried at December 31, 2011, Total	35,882,000	[2]
Accumulated Depreciation at December 31, 2011	24,898,000
Year of Construction	Jan. 01, 1975
Date of Acquisition	Aug. 01, 1979
Net Rentable Square Feet	221,000
Depreciation Life	41 years	[6]
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	5,125,000
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	9,056,000
Gross Amounts at Which Carried at December 31, 2011, Total	13,158,000	[2]
Accumulated Depreciation at December 31, 2011	4,662,000
Year of Construction	Jan. 01, 1966
Date of Acquisition	Jul. 01, 1992
Net Rentable Square Feet	74,000
Depreciation Life	50 years	[6]
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	11,947,000
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	23,873,000
Gross Amounts at Which Carried at December 31, 2011, Total	28,494,000	[2]
Accumulated Depreciation at December 31, 2011	15,372,000
Year of Construction	Jan. 01, 1971
Date of Acquisition	Jan. 01, 1995
Net Rentable Square Feet	202,000
Depreciation Life	30 years	[6]
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	9,690,000
Gross Amounts at Which Carried at December 31, 2011, Land	7,802,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	21,057,000
Gross Amounts at Which Carried at December 31, 2011, Total	28,859,000	[2]
Accumulated Depreciation at December 31, 2011	10,065,000
Year of Construction	Jan. 01, 1976
Date of Acquisition	Nov. 01, 1995
Net Rentable Square Feet	103,000
Depreciation Life	30 years	[6]
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	14,806,000
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	31,548,000
Gross Amounts at Which Carried at December 31, 2011, Total	38,209,000	[2]
Accumulated Depreciation at December 31, 2011	15,163,000
Year of Construction	Jan. 01, 1973
Date of Acquisition	Oct. 01, 1997
Net Rentable Square Feet	167,000
Depreciation Life	30 years	[6]
7900 Westpark Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	12,049,000	[1]
Initial Cost, Buildings and Improvements	71,825,000	[1]
Net Improvements (Retirement) since Acquisition	36,150,000
Gross Amounts at Which Carried at December 31, 2011, Land	12,049,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	107,975,000
Gross Amounts at Which Carried at December 31, 2011, Total	120,024,000	[2]
Accumulated Depreciation at December 31, 2011	56,264,000
Year of Construction	Jan. 01, 1972
Date of Acquisition	Nov. 01, 1997
Net Rentable Square Feet	538,000
Depreciation Life	30 years	[6]
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	5,512,000
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	17,700,000
Gross Amounts at Which Carried at December 31, 2011, Total	19,996,000	[2]
Accumulated Depreciation at December 31, 2011	8,346,000
Year of Construction	Jan. 01, 1985
Date of Acquisition	May 01, 1999
Net Rentable Square Feet	113,000
Depreciation Life	30 years	[6]
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	7,928,000
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	14,171,000
Gross Amounts at Which Carried at December 31, 2011, Total	15,735,000	[2]
Accumulated Depreciation at December 31, 2011	6,537,000
Year of Construction	Jan. 01, 1970
Date of Acquisition	May 01, 2000
Net Rentable Square Feet	96,000
Depreciation Life	30 years	[6]
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	6,677,000
Gross Amounts at Which Carried at December 31, 2011, Land	0
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	23,773,000
Gross Amounts at Which Carried at December 31, 2011, Total	23,773,000	[2]
Accumulated Depreciation at December 31, 2011	9,844,000
Year of Construction	Jan. 01, 1979
Date of Acquisition	Oct. 01, 2000
Net Rentable Square Feet	115,000
Depreciation Life	30 years	[6]
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	16,745,000
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	55,852,000
Gross Amounts at Which Carried at December 31, 2011, Total	61,332,000	[2]
Accumulated Depreciation at December 31, 2011	23,755,000
Year of Construction	Jan. 01, 1974
Date of Acquisition	Apr. 01, 2001
Net Rentable Square Feet	267,000
Depreciation Life	30 years	[6]
Atrium Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland
Initial Cost, Land	3,182,000	[1]
Initial Cost, Buildings and Improvements	11,281,000	[1]
Net Improvements (Retirement) since Acquisition	2,987,000
Gross Amounts at Which Carried at December 31, 2011, Land	3,182,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	14,268,000
Gross Amounts at Which Carried at December 31, 2011, Total	17,450,000	[2]
Accumulated Depreciation at December 31, 2011	5,922,000
Year of Construction	Jan. 01, 1980
Date of Acquisition	Jul. 01, 2002
Net Rentable Square Feet	79,000
Depreciation Life	30 years	[6]
Area of land	79,000
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	4,383,000
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	58,710,000
Gross Amounts at Which Carried at December 31, 2011, Total	90,210,000	[2]
Accumulated Depreciation at December 31, 2011	20,958,000
Year of Construction	Jan. 01, 1979
Date of Acquisition	Aug. 01, 2003
Net Rentable Square Feet	263,000
Depreciation Life	30 years	[6]
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	179,000	[8]
Date of Acquisition	Dec. 01, 2005	[8]
Net Rentable Square Feet	0	[8]
Land Placed In Service	500,000
6565 Arlington Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia	[5]
Initial Cost, Land	5,584,000	[1],[5]
Initial Cost, Buildings and Improvements	23,195,000	[1],[5]
Net Improvements (Retirement) since Acquisition	4,677,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	5,584,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	27,872,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	33,456,000	[2],[5]
Accumulated Depreciation at December 31, 2011	7,719,000	[5]
Year of Construction	Jan. 01, 1967	[5]
Date of Acquisition	Aug. 01, 2006	[5]
Net Rentable Square Feet	132,000
Depreciation Life	30 years	[5],[6]
West Gude Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland	[5]
Initial Cost, Land	11,580,000	[1],[5]
Initial Cost, Buildings and Improvements	43,240,000	[1],[5]
Net Improvements (Retirement) since Acquisition	8,208,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	11,580,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	51,448,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	63,028,000	[2],[5]
Accumulated Depreciation at December 31, 2011	12,807,000	[5]
Year of Construction	Jan. 01, 1984	[5]
Date of Acquisition	Aug. 01, 2006	[5]
Net Rentable Square Feet	275,000	[3],[5]
Depreciation Life	30 years	[5],[6]
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	3,737,000
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	68,942,000
Gross Amounts at Which Carried at December 31, 2011, Total	79,186,000	[2]
Accumulated Depreciation at December 31, 2011	15,247,000
Year of Construction	Jan. 01, 2000
Date of Acquisition	Mar. 01, 2007
Net Rentable Square Feet	207,000
Depreciation Life	30 years	[6]
Woodholme Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland
Initial Cost, Land	2,194,000	[1]
Initial Cost, Buildings and Improvements	16,711,000	[1]
Net Improvements (Retirement) since Acquisition	1,794,000
Gross Amounts at Which Carried at December 31, 2011, Land	2,194,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	18,505,000
Gross Amounts at Which Carried at December 31, 2011, Total	20,699,000	[2]
Accumulated Depreciation at December 31, 2011	4,039,000
Year of Construction	Jan. 01, 1989
Date of Acquisition	Jun. 01, 2007
Net Rentable Square Feet	80,000
Depreciation Life	30 years	[6]
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	16,427,000
Gross Amounts at Which Carried at December 31, 2011, Land	0
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	77,528,000
Gross Amounts at Which Carried at December 31, 2011, Total	77,528,000	[2]
Accumulated Depreciation at December 31, 2011	13,671,000
Year of Construction	Jan. 01, 1971
Date of Acquisition	Dec. 01, 2007
Net Rentable Square Feet	228,000
Depreciation Life	30 years	[6]
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	2,634,000	[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	109,377,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	156,264,000	[2],[5]
Accumulated Depreciation at December 31, 2011	17,462,000	[5]
Year of Construction	Jan. 01, 1986	[5]
Date of Acquisition	Dec. 01, 2008	[5]
Net Rentable Square Feet	290,000	[3],[5]
Depreciation Life	30 years	[5],[6]
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	165,000
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	24,966,000
Gross Amounts at Which Carried at December 31, 2011, Total	29,484,000	[2]
Accumulated Depreciation at December 31, 2011	3,692,000
Year of Construction	Jan. 01, 2007
Date of Acquisition	Jun. 01, 2010
Net Rentable Square Feet	134,000
Depreciation Life	30 years	[6]
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	126,000
Gross Amounts at Which Carried at December 31, 2011, Land	4,898,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	25,501,000
Gross Amounts at Which Carried at December 31, 2011, Total	30,399,000	[2]
Accumulated Depreciation at December 31, 2011	3,921,000
Year of Construction	Jan. 01, 2009
Date of Acquisition	Jun. 01, 2010
Net Rentable Square Feet	136,000
Depreciation Life	30 years	[6]
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	5,306,000
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	55,801,000
Gross Amounts at Which Carried at December 31, 2011, Total	81,027,000	[2]
Accumulated Depreciation at December 31, 2011	4,712,000
Year of Construction	Jan. 01, 1966
Date of Acquisition	Jan. 01, 2011
Net Rentable Square Feet	188,000
Depreciation Life	30 years	[6]
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	668,000
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	21,987,000
Gross Amounts at Which Carried at December 31, 2011, Total	39,492,000	[2]
Accumulated Depreciation at December 31, 2011	2,010,000
Year of Construction	Jan. 01, 1988
Date of Acquisition	Mar. 01, 2011
Net Rentable Square Feet	132,000
Depreciation Life	30 years	[6]
Braddock Place Member
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	18,817,000	[1],[5]
Initial Cost, Buildings and Improvements	71,250,000	[1]
Net Improvements (Retirement) since Acquisition	2,238,000
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	73,488,000
Gross Amounts at Which Carried at December 31, 2011, Total	92,305,000	[2]
Accumulated Depreciation at December 31, 2011	5,009,000
Year of Construction	Jan. 01, 1985
Date of Acquisition	Sep. 01, 2011
Net Rentable Square Feet	351,000
Depreciation Life	30 years	[6]
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	95,000	[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	53,119,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	66,609,000	[2],[5]
Accumulated Depreciation at December 31, 2011	2,856,000	[5]
Year of Construction	Jan. 01, 1996	[5]
Date of Acquisition	Sep. 01, 2011	[5]
Net Rentable Square Feet	223,000	[3],[5]
Depreciation Life	30 years	[5],[6]
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	284,000
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	30,169,000
Gross Amounts at Which Carried at December 31, 2011, Total	47,919,000	[2]
Accumulated Depreciation at December 31, 2011	895,000
Year of Construction	Jan. 01, 1988
Date of Acquisition	Jun. 01, 2012
Net Rentable Square Feet	142,000
Depreciation Life	30 years	[6]
Medical Office [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial Cost, Land	61,179,000	[1]
Initial Cost, Buildings and Improvements	308,148,000	[1]
Net Improvements (Retirement) since Acquisition	37,546,000
Gross Amounts at Which Carried at December 31, 2011, Land	61,225,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	345,647,000
Gross Amounts at Which Carried at December 31, 2011, Total	406,872,000	[2]
Accumulated Depreciation at December 31, 2011	95,797,000
Net Rentable Square Feet	1,285,000	[3]
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	4,328,000
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	16,788,000
Gross Amounts at Which Carried at December 31, 2011, Total	19,351,000	[2]
Accumulated Depreciation at December 31, 2011	8,105,000
Year of Construction	Jan. 01, 1984
Date of Acquisition	Nov. 01, 1998
Net Rentable Square Feet	73,000
Depreciation Life	30 years	[6]
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	4,310,000
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	21,884,000
Gross Amounts at Which Carried at December 31, 2011, Total	24,516,000	[2]
Accumulated Depreciation at December 31, 2011	10,261,000
Year of Construction	Jan. 01, 1988
Date of Acquisition	Nov. 01, 1998
Net Rentable Square Feet	96,000
Depreciation Life	30 years	[6]
8501 Arlington Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia	[5]
Initial Cost, Land	2,071,000	[1],[5]
Initial Cost, Buildings and Improvements	26,317,000	[1],[5]
Net Improvements (Retirement) since Acquisition	1,281,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	2,071,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	27,597,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	29,668,000	[2],[5]
Accumulated Depreciation at December 31, 2011	9,061,000	[5]
Year of Construction	Jan. 01, 2000	[5]
Date of Acquisition	Oct. 01, 2003	[5]
Net Rentable Square Feet	92,000	[3],[5]
Depreciation Life	30 years	[5],[6]
8503 Arlington Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia	[5]
Initial Cost, Land	1,598,000	[1],[5]
Initial Cost, Buildings and Improvements	25,850,000	[1],[5]
Net Improvements (Retirement) since Acquisition	1,478,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	1,598,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	27,328,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	28,926,000	[2],[5]
Accumulated Depreciation at December 31, 2011	8,754,000	[5]
Year of Construction	Jan. 01, 2001	[5]
Date of Acquisition	Oct. 01, 2003	[5]
Net Rentable Square Feet	88,000	[3],[5]
Depreciation Life	30 years	[5],[6]
8505 Arlington Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia	[5]
Initial Cost, Land	2,819,000	[1],[5]
Initial Cost, Buildings and Improvements	19,680,000	[1],[5]
Net Improvements (Retirement) since Acquisition	692,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	2,819,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	20,372,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	23,191,000	[2],[5]
Accumulated Depreciation at December 31, 2011	6,825,000	[5]
Year of Construction	Jan. 01, 2002	[5]
Date of Acquisition	Oct. 01, 2003	[5]
Net Rentable Square Feet	75,000	[3],[5]
Depreciation Life	30 years	[5],[6]
Shady Grove Medical Village Ii Member
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland
Initial Cost, Land	1,995,000	[1]
Initial Cost, Buildings and Improvements	16,601,000	[1]
Net Improvements (Retirement) since Acquisition	1,524,000
Gross Amounts at Which Carried at December 31, 2011, Land	1,995,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	18,125,000
Gross Amounts at Which Carried at December 31, 2011, Total	20,120,000	[2]
Accumulated Depreciation at December 31, 2011	5,129,000
Year of Construction	Jan. 01, 1999
Date of Acquisition	Aug. 01, 2004
Net Rentable Square Feet	66,000
Depreciation Life	30 years	[6]
8301 Arlington Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	1,251,000	[1]
Initial Cost, Buildings and Improvements	6,589,000	[1]
Net Improvements (Retirement) since Acquisition	1,766,000
Gross Amounts at Which Carried at December 31, 2011, Land	1,251,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	8,355,000
Gross Amounts at Which Carried at December 31, 2011, Total	9,606,000	[2]
Accumulated Depreciation at December 31, 2011	2,598,000
Year of Construction	Jan. 01, 1965
Date of Acquisition	Oct. 01, 2004
Net Rentable Square Feet	50,000
Depreciation Life	30 years	[6]
Alexandria Professional Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	6,783,000	[1]
Initial Cost, Buildings and Improvements	19,676,000	[1]
Net Improvements (Retirement) since Acquisition	5,955,000
Gross Amounts at Which Carried at December 31, 2011, Land	6,783,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	25,631,000
Gross Amounts at Which Carried at December 31, 2011, Total	32,414,000	[2]
Accumulated Depreciation at December 31, 2011	6,019,000
Year of Construction	Jan. 01, 1968
Date of Acquisition	Apr. 01, 2006
Net Rentable Square Feet	117,000
Depreciation Life	30 years	[6]
Medical Center Drive 9707 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland	[5]
Initial Cost, Land	3,069,000	[1],[5]
Initial Cost, Buildings and Improvements	11,777,000	[1],[5]
Net Improvements (Retirement) since Acquisition	1,151,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	3,069,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	12,928,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	15,997,000	[2],[5]
Accumulated Depreciation at December 31, 2011	3,246,000	[5]
Year of Construction	Jan. 01, 1994	[5]
Date of Acquisition	Apr. 01, 2006	[5]
Net Rentable Square Feet	38,000	[3],[5]
Depreciation Life	30 years	[5],[6]
15001 Shady Grove Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland
Initial Cost, Land	4,094,000	[1]
Initial Cost, Buildings and Improvements	16,410,000	[1]
Net Improvements (Retirement) since Acquisition	1,688,000
Gross Amounts at Which Carried at December 31, 2011, Land	4,094,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	18,098,000
Gross Amounts at Which Carried at December 31, 2011, Total	22,192,000	[2]
Accumulated Depreciation at December 31, 2011	4,694,000
Year of Construction	Jan. 01, 1999
Date of Acquisition	Apr. 01, 2006
Net Rentable Square Feet	51,000
Depreciation Life	30 years	[6]
Shady Grove Road 15005 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland	[5]
Initial Cost, Land	4,186,000	[1],[5]
Initial Cost, Buildings and Improvements	17,548,000	[1],[5]
Net Improvements (Retirement) since Acquisition	691,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	4,186,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	18,239,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	22,425,000	[2],[5]
Accumulated Depreciation at December 31, 2011	4,227,000	[5]
Year of Construction	Jan. 01, 2002	[5]
Date of Acquisition	Jul. 01, 2006	[5]
Net Rentable Square Feet	51,000	[3],[5]
Depreciation Life	30 years	[5],[6]
2440 M Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Washington, DC
Initial Cost, Land	12,500,000	[1]
Initial Cost, Buildings and Improvements	37,321,000	[1]
Net Improvements (Retirement) since Acquisition	5,099,000
Gross Amounts at Which Carried at December 31, 2011, Land	12,500,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	42,420,000
Gross Amounts at Which Carried at December 31, 2011, Total	54,920,000	[2]
Accumulated Depreciation at December 31, 2011	9,787,000
Year of Construction	Jan. 01, 1986
Date of Acquisition	Mar. 01, 2007
Net Rentable Square Feet	113,000
Depreciation Life	30 years	[6]
Woodholme Medical Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland	[5]
Initial Cost, Land	3,744,000	[1],[5]
Initial Cost, Buildings and Improvements	24,587,000	[1],[5]
Net Improvements (Retirement) since Acquisition	2,015,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	3,744,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	26,602,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	30,346,000	[2],[5]
Accumulated Depreciation at December 31, 2011	5,881,000	[5]
Year of Construction	Jan. 01, 1996	[5]
Date of Acquisition	Jun. 01, 2007	[5]
Net Rentable Square Feet	127,000	[3],[5]
Depreciation Life	30 years	[5],[6]
Ashburn Farm Professional Cntr [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia	[5]
Initial Cost, Land	3,770,000	[1],[5]
Initial Cost, Buildings and Improvements	19,200,000	[1],[5]
Net Improvements (Retirement) since Acquisition	1,458,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	3,770,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	20,658,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	24,428,000	[2],[5]
Accumulated Depreciation at December 31, 2011	4,412,000	[5]
Year of Construction	Jan. 01, 1998	[5]
Date of Acquisition	Jun. 01, 2007	[5]
Net Rentable Square Feet	75,000	[3],[5]
Depreciation Life	30 years	[5],[6]
CentreMed I & II [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	2,062,000	[1]
Initial Cost, Buildings and Improvements	12,506,000	[1]
Net Improvements (Retirement) since Acquisition	759,000
Gross Amounts at Which Carried at December 31, 2011, Land	2,062,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	13,265,000
Gross Amounts at Which Carried at December 31, 2011, Total	15,327,000	[2]
Accumulated Depreciation at December 31, 2011	2,703,000
Year of Construction	Jan. 01, 1998
Date of Acquisition	Aug. 01, 2007
Net Rentable Square Feet	52,000
Depreciation Life	30 years	[6]
4661 Kenmore Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia	[8]
Initial Cost, Land	3,764,000	[1],[8]
Initial Cost, Buildings and Improvements	0	[1],[8]
Net Improvements (Retirement) since Acquisition	46,000	[8]
Gross Amounts at Which Carried at December 31, 2011, Land	3,810,000	[8]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	0	[8]
Gross Amounts at Which Carried at December 31, 2011, Total	3,810,000	[2],[8]
Accumulated Depreciation at December 31, 2011	0	[8]
Date of Acquisition	Aug. 01, 2007	[8]
Area of land	0.8
Sterling Medical Office Bldg [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	970,000	[1]
Initial Cost, Buildings and Improvements	5,274,000	[1]
Net Improvements (Retirement) since Acquisition	895,000
Gross Amounts at Which Carried at December 31, 2011, Land	970,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	6,169,000
Gross Amounts at Which Carried at December 31, 2011, Total	7,139,000	[2]
Accumulated Depreciation at December 31, 2011	1,434,000
Year of Construction	Jan. 01, 1986
Date of Acquisition	May 01, 2008
Net Rentable Square Feet	36,000
Depreciation Life	30 years	[6]
Lansdowne Medical Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Virginia
Initial Cost, Land	1,308,000	[1]
Initial Cost, Buildings and Improvements	18,778,000	[1]
Net Improvements (Retirement) since Acquisition	2,410,000
Gross Amounts at Which Carried at December 31, 2011, Land	1,308,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	21,188,000
Gross Amounts at Which Carried at December 31, 2011, Total	22,496,000	[2]
Accumulated Depreciation at December 31, 2011	2,661,000
Year of Construction	Jan. 01, 2009
Date of Acquisition	Aug. 01, 2009
Net Rentable Square Feet	85,000
Depreciation Life	30 years	[6]
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	64,414,000
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	290,201,000
Gross Amounts at Which Carried at December 31, 2011, Total	412,537,000	[2]
Accumulated Depreciation at December 31, 2011	85,220,000
Net Rentable Square Feet	2,448,000	[3]
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	155,000
Gross Amounts at Which Carried at December 31, 2011, Land	415,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	1,239,000
Gross Amounts at Which Carried at December 31, 2011, Total	1,654,000	[2]
Accumulated Depreciation at December 31, 2011	1,170,000
Year of Construction	Jan. 01, 1962
Date of Acquisition	Jul. 01, 1963
Net Rentable Square Feet	51,000
Depreciation Life	50 years	[6]
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	9,140,000
Gross Amounts at Which Carried at December 31, 2011, Land	519,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	10,915,000
Gross Amounts at Which Carried at December 31, 2011, Total	11,434,000	[2]
Accumulated Depreciation at December 31, 2011	6,183,000
Year of Construction	Jan. 01, 1969
Date of Acquisition	Sep. 01, 1972
Net Rentable Square Feet	150,000
Depreciation Life	37 years	[6]
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	3,437,000
Gross Amounts at Which Carried at December 31, 2011, Land	413,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	4,287,000
Gross Amounts at Which Carried at December 31, 2011, Total	4,700,000	[2]
Accumulated Depreciation at December 31, 2011	2,885,000
Year of Construction	Jan. 01, 1960
Date of Acquisition	Dec. 01, 1973
Net Rentable Square Feet	76,000
Depreciation Life	33 years	[6]
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	4,526,000
Gross Amounts at Which Carried at December 31, 2011, Land	796,000
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	5,383,000
Gross Amounts at Which Carried at December 31, 2011, Total	6,179,000	[2]
Accumulated Depreciation at December 31, 2011	3,207,000
Year of Construction	Jan. 01, 1967
Date of Acquisition	Sep. 01, 1977
Net Rentable Square Feet	74,000
Depreciation Life	50 years	[6]
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	8,114,000
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	13,497,000
Gross Amounts at Which Carried at December 31, 2011, Total	17,649,000	[2]
Accumulated Depreciation at December 31, 2011	9,216,000
Year of Construction	Jan. 01, 1955
Date of Acquisition	Dec. 01, 1984
Net Rentable Square Feet	168,000
Depreciation Life	40 years	[6]
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	4,870,000
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	9,174,000
Gross Amounts at Which Carried at December 31, 2011, Total	10,723,000	[2]
Accumulated Depreciation at December 31, 2011	5,698,000
Year of Construction	Jan. 01, 1975
Date of Acquisition	Sep. 01, 1985
Net Rentable Square Feet	49,000
Depreciation Life	50 years	[6]
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	3,178,000
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	12,283,000
Gross Amounts at Which Carried at December 31, 2011, Total	23,908,000	[2]
Accumulated Depreciation at December 31, 2011	5,139,000
Year of Construction	Jan. 01, 1969
Date of Acquisition	Dec. 01, 1992
Net Rentable Square Feet	197,000
Depreciation Life	50 years	[6]
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	13,135,000
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	16,114,000
Gross Amounts at Which Carried at December 31, 2011, Total	21,952,000	[2]
Accumulated Depreciation at December 31, 2011	4,829,000
Year of Construction	Jan. 01, 1960
Date of Acquisition	Jun. 01, 1994
Net Rentable Square Feet	134,000
Depreciation Life	50 years	[6]
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	3,169,000
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	9,999,000
Gross Amounts at Which Carried at December 31, 2011, Total	16,560,000	[2]
Accumulated Depreciation at December 31, 2011	5,958,000
Year of Construction	Jan. 01, 1973
Date of Acquisition	Aug. 01, 1995
Net Rentable Square Feet	227,000
Depreciation Life	30 years	[6]
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	5,992,000
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	11,481,000
Gross Amounts at Which Carried at December 31, 2011, Total	14,385,000	[2]
Accumulated Depreciation at December 31, 2011	3,714,000
Year of Construction	Jan. 01, 1951
Date of Acquisition	Jun. 01, 1998
Net Rentable Square Feet	47,000
Depreciation Life	30 years	[6]
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	2,165,000
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	27,580,000
Gross Amounts at Which Carried at December 31, 2011, Total	40,609,000	[2]
Accumulated Depreciation at December 31, 2011	9,815,000
Year of Construction	Jan. 01, 2000
Date of Acquisition	Jun. 01, 2002
Net Rentable Square Feet	332,000
Depreciation Life	30 years	[6]
Frederick Crossing [Member]
Real Estate and Accumulated Depreciation [Line Items]
Location	Maryland	[5]
Initial Cost, Land	12,759,000	[1],[5]
Initial Cost, Buildings and Improvements	35,477,000	[1],[5]
Net Improvements (Retirement) since Acquisition	2,127,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Land	12,759,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Buildings and Improvements	37,604,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	50,363,000	[2],[5]
Accumulated Depreciation at December 31, 2011	10,319,000	[5]
Year of Construction	Jan. 01, 1999	[5]
Date of Acquisition	Mar. 01, 2005	[5]
Net Rentable Square Feet	295,000	[3],[5]
Depreciation Life	30 years	[5],[6]
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	650,000
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	13,675,000
Gross Amounts at Which Carried at December 31, 2011, Total	18,603,000	[2]
Accumulated Depreciation at December 31, 2011	3,366,000
Year of Construction	Jan. 01, 1972
Date of Acquisition	May 01, 2006
Net Rentable Square Feet	82,000
Depreciation Life	30 years	[6]
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	2,529,000
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	24,939,000
Gross Amounts at Which Carried at December 31, 2011, Total	36,551,000	[2]
Accumulated Depreciation at December 31, 2011	6,009,000
Year of Construction	Jan. 01, 1970
Date of Acquisition	May 01, 2006
Net Rentable Square Feet	145,000
Depreciation Life	30 years	[6]
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	335,000
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	52,006,000
Gross Amounts at Which Carried at December 31, 2011, Total	81,400,000	[2]
Accumulated Depreciation at December 31, 2011	5,588,000
Year of Construction	Jan. 01, 2007
Date of Acquisition	Dec. 01, 2010
Net Rentable Square Feet	223,000
Depreciation Life	30 years	[6]
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	892,000	[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	40,025,000	[5]
Gross Amounts at Which Carried at December 31, 2011, Total	55,867,000	[2],[5]
Accumulated Depreciation at December 31, 2011	2,124,000	[5]
Year of Construction	Jan. 01, 1979	[5]
Date of Acquisition	Aug. 01, 2011	[5]
Net Rentable Square Feet	198,000	[3],[5]
Depreciation Life	30 years	[5],[6]
3801 Connecticut [Member]
Real Estate and Accumulated Depreciation [Line Items]
Secured Debt	35,399,000
Kenmore Apartments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Mortgage notes payable	35,535,000		36,097,000
Walker House Apartments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Secured Debt	16,531,000
West Gude Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Mortgage notes payable	29,996,000		30,761,000
Olney Village Center Member
Real Estate and Accumulated Depreciation [Line Items]
Mortgage notes payable	22,343,000		23,873,000
Bethesda Hill Apartments [Member]
Real Estate and Accumulated Depreciation [Line Items]
Secured Debt	29,099,000
John Marshall II Member
Real Estate and Accumulated Depreciation [Line Items]
Mortgage notes payable	53,274,000		53,936,000
M Street 2445 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Mortgage notes payable	96,848,000	[9]	95,593,000	[9]
Ashburn Farm Professional Cntr [Member]
Real Estate and Accumulated Depreciation [Line Items]
Secured Debt	4,337,000
Woodholme Medical Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Mortgage notes payable	$ 19,608,000		$ 19,954,000
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, 2012, total land, buildings and improvements are carried at $2,148,544,000 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, 2012, our properties were encumbered by non-recourse mortgage amounts as follows: $35,399,000 on 3801 Connecticut Avenue, $16,531,000 on Walker House, $29,099,000 on Bethesda Hill, $35,535,000 on The Kenmore, $29,996,000 on West Gude Drive, $96,848,000 on 2445 M Street, $53,274,000 on John Marshall II, $19,608,000 on Woodholme Medical Center, $4,337,000 on Ashburn Farm, and $22,343,000 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, 2012, 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 total value not yet placed into service of these development projects via joint venture arrangements at December 31, 2012 was $35.5 million. [8] As of December 31, 2012, WRIT had land held for development in Herndon, VA (Dulles Station, Phase II). WRIT also held a 0.8 acre parcel of land at 4661 Kenmore for future development. Additionally, WRIT had investments in various smaller development or redevelopment projects. The total land value not yet placed in service of these development projects at December 31, 2012 was $7.5 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. [9] Interest only is payable monthly until the maturity date upon which all unpaid principal and interest are payable in full.