Real Estate and Accumulated Depreciation Schedule of Real Estate and Accumulated Depreciation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Real Estate and Accumulated Depreciation [Line Items]
Type	Office
Location	Reston, VA
Encumbrances	$ 3,102,485,000	[1]
Original Land	2,500,010,000
Original Building	9,097,935,000
Costs Capitalized Subsequent to Acquisition	3,271,942,000
Land and improvements	2,605,162,000
Buildings and Improvements	10,952,851,000
Land Held for Development	275,094,000
Development and Construction in Progress	1,036,780,000
Total	14,869,887,000
Accumulated Depreciation	2,919,479,000
Depreciable Lives (Years)	-1	[2]
Furniture, fixtures and equipment	23,441,000		26,359,000
Furniture, fixtures and equipment accumulated depreciation	16,662,000
Real Estate Aggregate Cost For Tax Purposes	12,200,000,000
Real Estate Aggregate Accumulated Depreciation For Tax Purposes	2,200,000,000
Real Estate and Accumulated Depreciation, Life Used for Depreciation	40 years 0 months 0 days
Unamoritized balance of histroical fair value adjustments	38,644,000
Embarcadero Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Embarcadero Center
Type	Office
Location	San Francisco, CA
Encumbrances	365,263,000
Original Land	179,697,000
Original Building	847,410,000
Costs Capitalized Subsequent to Acquisition	299,360,000
Land and improvements	195,984,000
Buildings and Improvements	1,130,483,000
Land Held for Development	0
Total	1,326,467,000
Accumulated Depreciation	431,933,000
Year(s) built / renovated	1970/1989
Depreciable Lives (Years)	-1
Prudential Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Prudential Center
Type	Office
Location	Boston, MA
Original Land	92,077,000
Original Building	734,594,000
Costs Capitalized Subsequent to Acquisition	339,363,000
Land and improvements	107,426,000
Buildings and Improvements	1,042,589,000
Land Held for Development	16,019,000
Total	1,166,034,000
Accumulated Depreciation	363,098,000
Year(s) built / renovated	1965/1993/2002
Depreciable Lives (Years)	-1
399 Park Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	399 Park Avenue
Type	Office
Location	New York, NY
Original Land	339,200,000
Original Building	700,358,000
Costs Capitalized Subsequent to Acquisition	91,986,000
Land and improvements	354,107,000
Buildings and Improvements	777,437,000
Land Held for Development	0
Total	1,131,544,000
Accumulated Depreciation	197,783,000
Year(s) built / renovated	1961
Depreciable Lives (Years)	-1
601 Lexington Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	601 Lexington Avenue
Type	Office
Location	New York, NY
Encumbrances	725,000,000
Original Land	241,600,000
Original Building	494,782,000
Costs Capitalized Subsequent to Acquisition	216,384,000
Land and improvements	289,639,000
Buildings and Improvements	663,127,000
Land Held for Development	0
Total	952,766,000
Accumulated Depreciation	184,225,000
Year(s) built / renovated	1977/1997
Depreciable Lives (Years)	-1
The John Hancock Tower And Garage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	The John Hancock Tower and Garage
Type	Office
Location	Boston, MA
Encumbrances	656,572,000
Original Land	219,543,000
Original Building	667,884,000
Costs Capitalized Subsequent to Acquisition	43,528,000
Land and improvements	219,616,000
Buildings and Improvements	711,339,000
Land Held for Development	0
Total	930,955,000
Accumulated Depreciation	51,483,000
Year(s) built / renovated	1976
Depreciable Lives (Years)	-1
Times Square Tower [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Times Square Tower
Type	Office
Location	New York, NY
Original Land	165,413,000
Original Building	380,438,000
Costs Capitalized Subsequent to Acquisition	84,227,000
Land and improvements	169,193,000
Buildings and Improvements	460,885,000
Land Held for Development	0
Total	630,078,000
Accumulated Depreciation	124,896,000
Year(s) built / renovated	2004
Depreciable Lives (Years)	-1
100 Federal Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	100 Federal Street
Type	Office
Location	Boston, MA
Original Land	131,067,000
Original Building	435,954,000
Costs Capitalized Subsequent to Acquisition	566,000
Land and improvements	131,067,000
Buildings and Improvements	436,520,000
Total	567,587,000
Accumulated Depreciation	12,712,000
Year(s) built / renovated	1971-1975
Depreciable Lives (Years)	-1	[2]
Carnegie Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Carnegie Center
Type	Office
Location	Princeton, NJ
Original Land	105,107,000
Original Building	377,259,000
Costs Capitalized Subsequent to Acquisition	59,196,000
Land and improvements	103,062,000
Buildings and Improvements	436,434,000
Land Held for Development	2,066,000
Total	541,562,000
Accumulated Depreciation	155,643,000
Year(s) built / renovated	1983-1999/2009
Depreciable Lives (Years)	-1
Atlantic Wharf [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Atlantic Wharf
Type	Office
Location	Boston, MA
Original Land	63,988,000
Original Building	454,537,000
Costs Capitalized Subsequent to Acquisition	8,735,000
Land and improvements	63,988,000
Buildings and Improvements	463,272,000
Land Held for Development	0
Total	527,260,000
Accumulated Depreciation	24,700,000
Year(s) built / renovated	2011
Depreciable Lives (Years)	-1	[2]
Fountain Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Fountain Square
Type	Office
Location	Reston, VA
Encumbrances	232,916,000
Original Land	56,853,000
Original Building	306,298,000
Costs Capitalized Subsequent to Acquisition	825,000
Land and improvements	56,853,000
Buildings and Improvements	307,123,000
Total	363,976,000
Accumulated Depreciation	3,088,000
Year(s) built / renovated	1986-1990
Depreciable Lives (Years)	-1	[2]
510 Madison Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	510 Madison Avenue
Type	Office
Location	New York, NY
Original Land	103,000,000
Original Building	253,665,000
Costs Capitalized Subsequent to Acquisition	0
Land and improvements	103,000,000
Buildings and Improvements	253,665,000
Total	356,665,000
Accumulated Depreciation	7,485,000
Year(s) built / renovated	2012
Depreciable Lives (Years)	-1	[2]
599 Lexington Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	599 Lexington Avenue
Type	Office
Location	New York, NY
Encumbrances	750,000,000
Original Land	81,040,000
Original Building	100,507,000
Costs Capitalized Subsequent to Acquisition	120,936,000
Land and improvements	87,852,000
Buildings and Improvements	214,631,000
Land Held for Development	0
Total	302,483,000
Accumulated Depreciation	138,001,000
Year(s) built / renovated	1986
Depreciable Lives (Years)	-1
Gateway Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Gateway Center
Type	Office
Location	San Francisco, CA
Original Land	28,255,000
Original Building	139,245,000
Costs Capitalized Subsequent to Acquisition	50,792,000
Land and improvements	30,627,000
Buildings and Improvements	187,665,000
Land Held for Development	0
Total	218,292,000
Accumulated Depreciation	72,672,000
Year(s) built / renovated	1984/1986/2002
Depreciable Lives (Years)	-1
Bay Colony Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Bay Colony Corporate Center
Type	Office
Location	Waltham, MA
Original Land	18,789,000
Original Building	148,451,000
Costs Capitalized Subsequent to Acquisition	25,031,000
Land and improvements	18,789,000
Buildings and Improvements	173,482,000
Land Held for Development	0
Total	192,271,000
Accumulated Depreciation	13,499,000
Year(s) built / renovated	1985-1989
Depreciable Lives (Years)	-1	[2]
South of Market [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	South of Market
Type	Office
Location	Reston, VA
Original Land	13,603,000
Original Building	164,144,000
Costs Capitalized Subsequent to Acquisition	9,359,000
Land and improvements	13,687,000
Buildings and Improvements	173,419,000
Total	187,106,000
Accumulated Depreciation	31,984,000
Year(s) built / renovated	2008
Depreciable Lives (Years)	-1
2200 Pennsylvania Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	2200 Pennsylvania Avenue
Type	Office
Location	Washington, DC
Original Building	183,541,000
Costs Capitalized Subsequent to Acquisition	2,274,000
Land and improvements	0
Buildings and Improvements	185,815,000
Land Held for Development	0
Total	185,815,000
Accumulated Depreciation	11,068,000
Year(s) built / renovated	2011
Depreciable Lives (Years)	-1
One Patriots Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	One Patriots Park (formerly known as 12310 Sunrise Valley Drive)
Original Land	9,367,000
Original Building	67,431,000
Costs Capitalized Subsequent to Acquisition	63,039,000
Land and improvements	11,343,000
Buildings and Improvements	128,494,000
Land Held for Development	0
Total	139,837,000
Accumulated Depreciation	50,376,000
Year(s) built / renovated	1987/1988/2012
Depreciable Lives (Years)	-1	[2]
Reservoir Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Reservoir Place
Type	Office
Location	Waltham, MA
Original Land	18,605,000
Original Building	92,619,000
Costs Capitalized Subsequent to Acquisition	26,487,000
Land and improvements	20,118,000
Buildings and Improvements	117,593,000
Land Held for Development	0
Total	137,711,000
Accumulated Depreciation	48,183,000
Year(s) built / renovated	1955/1987
Depreciable Lives (Years)	-1
3200 Zanker Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	3200 Zanker Road
Type	Office
Location	San Jose, CA
Original Land	36,705,000
Original Building	82,863,000
Costs Capitalized Subsequent to Acquisition	15,492,000
Land and improvements	36,997,000
Buildings and Improvements	94,320,000
Land Held for Development	3,743,000
Total	135,060,000
Accumulated Depreciation	20,684,000
Year(s) built / renovated	1988
Depreciable Lives (Years)	-1	[2]
505 9th Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	505 9th Street
Type	Office
Location	Washington, DC
Encumbrances	123,666,000
Original Land	38,885,000
Original Building	83,719,000
Costs Capitalized Subsequent to Acquisition	5,692,000
Land and improvements	42,082,000
Buildings and Improvements	86,214,000
Land Held for Development	0
Total	128,296,000
Accumulated Depreciation	17,117,000
Year(s) built / renovated	2007
Depreciable Lives (Years)	-1
1333 New Hampshire Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	1333 New Hampshire Avenue
Type	Office
Location	Washington, DC
Original Land	34,032,000
Original Building	85,660,000
Costs Capitalized Subsequent to Acquisition	8,407,000
Land and improvements	35,382,000
Buildings and Improvements	92,717,000
Land Held for Development	0
Total	128,099,000
Accumulated Depreciation	27,928,000
Year(s) built / renovated	1996
Depreciable Lives (Years)	-1
Kingstowne Towne Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Kingstowne Towne Center
Type	Office
Location	Alexandria, VA
Encumbrances	52,292,000
Original Land	18,021,000
Original Building	109,038,000
Costs Capitalized Subsequent to Acquisition	174,000
Land and improvements	18,062,000
Buildings and Improvements	109,171,000
Land Held for Development	0
Total	127,233,000
Accumulated Depreciation	22,981,000
Year(s) built / renovated	2003-2006
Depreciable Lives (Years)	-1
Capital Gallery [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Capital Gallery
Type	Office
Location	Washington, DC
Original Land	4,725,000
Original Building	29,565,000
Costs Capitalized Subsequent to Acquisition	90,761,000
Land and improvements	8,662,000
Buildings and Improvements	116,389,000
Land Held for Development	0
Total	125,051,000
Accumulated Depreciation	50,572,000
Year(s) built / renovated	1981/2006
Depreciable Lives (Years)	-1	[2]
1330 Connecticut Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	1330 Connecticut Avenue
Type	Office
Location	Washington, DC
Original Land	25,982,000
Original Building	82,311,000
Costs Capitalized Subsequent to Acquisition	16,248,000
Land and improvements	27,135,000
Buildings and Improvements	97,406,000
Land Held for Development	0
Total	124,541,000
Accumulated Depreciation	26,291,000
Year(s) built / renovated	1984
Depreciable Lives (Years)	-1
601 Massachusetts Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	601 Massachusetts Avenue
Type	Office
Location	Washington, DC
Original Land	95,281,000
Original Building	22,221,000
Costs Capitalized Subsequent to Acquisition	4,300,000
Land and improvements	95,293,000
Buildings and Improvements	22,257,000
Land Held for Development	4,252,000
Total	121,802,000
Accumulated Depreciation	18,123,000
Year(s) built / renovated	1968/1992
Depreciable Lives (Years)	-1
Weston Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Weston Corporate Center
Type	Office
Location	Weston, MA
Original Land	25,753,000
Original Building	92,312,000
Costs Capitalized Subsequent to Acquisition	(149,000)
Land and improvements	25,852,000
Buildings and Improvements	92,064,000
Land Held for Development	0
Total	117,916,000
Accumulated Depreciation	7,870,000
Year(s) built / renovated	2010
Depreciable Lives (Years)	-1
One Freedom Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	One Freedom Square
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	9,929,000
Original Building	84,504,000
Costs Capitalized Subsequent to Acquisition	22,960,000
Land and improvements	11,293,000
Buildings and Improvements	106,100,000
Land Held for Development	0
Total	117,393,000
Accumulated Depreciation	39,586,000
Year(s) built / renovated	2000
Depreciable Lives (Years)	-1	[2]
One And Two Reston Overlook [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	One and Two Reston Overlook
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	16,456,000
Original Building	66,192,000
Costs Capitalized Subsequent to Acquisition	23,463,000
Land and improvements	17,561,000
Buildings and Improvements	88,550,000
Land Held for Development	0
Total	106,111,000
Accumulated Depreciation	26,959,000
Year(s) built / renovated	1999
Depreciable Lives (Years)	-1	[2]
Two Freedom Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Two Freedom Square
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	13,930,000
Original Building	77,739,000
Costs Capitalized Subsequent to Acquisition	13,797,000
Land and improvements	15,420,000
Buildings and Improvements	90,046,000
Land Held for Development	0
Total	105,466,000
Accumulated Depreciation	34,233,000
Year(s) built / renovated	2001
Depreciable Lives (Years)	-1	[2]
Seven Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Seven Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	3,457,000
Original Building	97,136,000
Costs Capitalized Subsequent to Acquisition	2,880,000
Land and improvements	4,125,000
Buildings and Improvements	99,348,000
Land Held for Development	0
Total	103,473,000
Accumulated Depreciation	41,528,000
Year(s) built / renovated	2006
Depreciable Lives (Years)	-1	[2]
Discovery Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Discovery Square
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	11,198,000
Original Building	71,782,000
Costs Capitalized Subsequent to Acquisition	15,501,000
Land and improvements	12,533,000
Buildings and Improvements	85,948,000
Land Held for Development	0
Total	98,481,000
Accumulated Depreciation	25,842,000
Year(s) built / renovated	2001
Depreciable Lives (Years)	-1	[2]
140 Kendrick Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	140 Kendrick Street
Type	Office
Location	Needham, MA
Encumbrances	48,358,000
Original Land	18,095,000
Original Building	66,905,000
Costs Capitalized Subsequent to Acquisition	8,424,000
Land and improvements	19,092,000
Buildings and Improvements	74,332,000
Land Held for Development	0
Total	93,424,000
Accumulated Depreciation	15,474,000
Year(s) built / renovated	2000
Depreciable Lives (Years)	-1	[2]
Five Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Five Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	18,863,000
Original Building	53,346,000
Costs Capitalized Subsequent to Acquisition	19,288,000
Land and improvements	18,938,000
Buildings and Improvements	63,619,000
Land Held for Development	0
Total	91,497,000
Accumulated Depreciation	17,480,000
Year(s) built / renovated	1981/1996
Depreciable Lives (Years)	-1	[2]
77 CityPoint [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	77 CityPoint
Type	Office
Location	Waltham, MA
Encumbrances	0
Original Land	13,847,000
Original Building	60,383,000
Costs Capitalized Subsequent to Acquisition	3,123,000
Land and improvements	13,875,000
Buildings and Improvements	63,478,000
Land Held for Development	0
Total	77,353,000
Accumulated Depreciation	9,936,000
Year(s) built / renovated	2008
Depreciable Lives (Years)	-1	[2]
North First Business Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	North First Business Park
Type	Office
Location	San Jose, CA
Encumbrances	0
Original Land	58,402,000
Original Building	13,069,000
Costs Capitalized Subsequent to Acquisition	3,793,000
Land and improvements	23,377,000
Buildings and Improvements	16,010,000
Land Held for Development	35,877,000
Total	75,264,000
Accumulated Depreciation	8,217,000
Year(s) built / renovated	1981
Depreciable Lives (Years)	-1	[2]
230 CityPoint [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	230 CityPoint
Type	Office
Location	Waltham, MA
Encumbrances	0
Original Land	13,189,000
Original Building	49,823,000
Costs Capitalized Subsequent to Acquisition	11,694,000
Land and improvements	13,593,000
Buildings and Improvements	61,113,000
Land Held for Development	0
Total	74,706,000
Accumulated Depreciation	15,128,000
Year(s) built / renovated	1992
Depreciable Lives (Years)	-1	[2]
Four Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Four Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	19,104,000
Original Building	52,078,000
Costs Capitalized Subsequent to Acquisition	3,514,000
Land and improvements	19,148,000
Buildings and Improvements	55,548,000
Land Held for Development	0
Total	74,696,000
Accumulated Depreciation	9,118,000
Year(s) built / renovated	1983/1998
Depreciable Lives (Years)	-1	[2]
Waltham Weston Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Waltham Weston Corporate Center
Type	Office
Location	Waltham, MA
Encumbrances	0
Original Land	10,385,000
Original Building	60,694,000
Costs Capitalized Subsequent to Acquisition	2,987,000
Land and improvements	11,097,000
Buildings and Improvements	62,969,000
Land Held for Development	0
Total	74,066,000
Accumulated Depreciation	19,278,000
Year(s) built / renovated	2003
Depreciable Lives (Years)	-1	[2]
Democracy Tower [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Democracy Tower
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	0
Original Building	73,335,000
Costs Capitalized Subsequent to Acquisition	431,000
Land and improvements	0
Buildings and Improvements	73,766,000
Land Held for Development	0
Total	73,766,000
Accumulated Depreciation	8,914,000
Year(s) built / renovated	2009
Depreciable Lives (Years)	-1	[2]
2440 West El Camino Real [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	2440 West El Camino Real
Type	Office
Location	Mountain View, CA
Encumbrances	0
Original Land	16,741,000
Original Building	51,285,000
Costs Capitalized Subsequent to Acquisition	491,000
Land and improvements	16,741,000
Buildings and Improvements	51,776,000
Land Held for Development	0
Total	68,517,000
Accumulated Depreciation	2,268,000
Year(s) built / renovated	1987/2003
Depreciable Lives (Years)	-1	[2]
Wisconsin Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Wisconsin Place
Type	Office
Location	Chevy Chase, MD
Encumbrances	0
Original Land	0
Original Building	53,349,000
Costs Capitalized Subsequent to Acquisition	13,661,000
Land and improvements	0
Buildings and Improvements	67,010,000
Land Held for Development	0
Total	67,010,000
Accumulated Depreciation	8,838,000
Year(s) built / renovated	2009
Depreciable Lives (Years)	-1	[2]
Reston Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Reston Corporate Center
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	9,135,000
Original Building	50,857,000
Costs Capitalized Subsequent to Acquisition	5,334,000
Land and improvements	10,148,000
Buildings and Improvements	55,178,000
Land Held for Development	0
Total	65,326,000
Accumulated Depreciation	19,527,000
Year(s) built / renovated	1984
Depreciable Lives (Years)	-1	[2]
New Dominion Technology Park, Bldg. Two [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	New Dominion Technology Park, Bldg. Two
Type	Office
Location	Herndon, VA
Encumbrances	63,000,000
Original Land	5,584,000
Original Building	51,868,000
Costs Capitalized Subsequent to Acquisition	3,894,000
Land and improvements	6,510,000
Buildings and Improvements	54,836,000
Land Held for Development	0
Total	61,346,000
Accumulated Depreciation	14,760,000
Year(s) built / renovated	2004
Depreciable Lives (Years)	-1	[2]
One Preserve Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	One Preserve Parkway
Type	Office
Location	Rockville, MD
Encumbrances	0
Original Land	5,357,000
Original Building	42,186,000
Costs Capitalized Subsequent to Acquisition	8,699,000
Land and improvements	5,357,000
Buildings and Improvements	50,885,000
Land Held for Development	0
Total	56,242,000
Accumulated Depreciation	6,768,000
Year(s) built / renovated	2009
Depreciable Lives (Years)	-1	[2]
Sumner Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Sumner Square
Type	Office
Location	Washington, DC
Encumbrances	0
Original Land	624,000
Original Building	28,745,000
Costs Capitalized Subsequent to Acquisition	23,161,000
Land and improvements	1,478,000
Buildings and Improvements	51,052,000
Land Held for Development	0
Total	52,530,000
Accumulated Depreciation	21,422,000
Year(s) built / renovated	1985
Depreciable Lives (Years)	-1	[2]
New Dominion Technology Park, Bldg. One [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	New Dominion Technology Park, Bldg. One
Type	Office
Location	Herndon, VA
Encumbrances	45,418,000
Original Land	3,880,000
Original Building	43,227,000
Costs Capitalized Subsequent to Acquisition	3,882,000
Land and improvements	4,583,000
Buildings and Improvements	46,406,000
Land Held for Development	0
Total	50,989,000
Accumulated Depreciation	17,984,000
Year(s) built / renovated	2001
Depreciable Lives (Years)	-1	[2]
303 Almaden [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	303 Almaden Boulevard
Type	Office
Location	San Jose, CA
Encumbrances	0
Original Land	10,836,000
Original Building	35,606,000
Costs Capitalized Subsequent to Acquisition	4,060,000
Land and improvements	10,947,000
Buildings and Improvements	39,555,000
Land Held for Development	0
Total	50,502,000
Accumulated Depreciation	8,994,000
Year(s) built / renovated	1995
Depreciable Lives (Years)	-1	[2]
200 West Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	200 West Street
Type	Office
Location	Waltham, MA
Encumbrances	0
Original Land	16,148,000
Original Building	24,983,000
Costs Capitalized Subsequent to Acquisition	8,100,000
Land and improvements	16,813,000
Buildings and Improvements	32,418,000
Land Held for Development	0
Total	49,231,000
Accumulated Depreciation	13,499,000
Year(s) built / renovated	1999
Depreciable Lives (Years)	-1	[2]
1301 New York Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	1301 New York Avenue
Type	Office
Location	Washington, DC
Encumbrances	0
Original Land	9,250,000
Original Building	18,750,000
Costs Capitalized Subsequent to Acquisition	20,590,000
Land and improvements	9,867,000
Buildings and Improvements	38,723,000
Land Held for Development	0
Total	48,590,000
Accumulated Depreciation	15,486,000
Year(s) built / renovated	1983/1998
Depreciable Lives (Years)	-1	[2]
191 Spring Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	191 Spring Street
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	2,850,000
Original Building	27,166,000
Costs Capitalized Subsequent to Acquisition	18,403,000
Land and improvements	3,151,000
Buildings and Improvements	45,268,000
Land Held for Development	0
Total	48,419,000
Accumulated Depreciation	28,197,000
Year(s) built / renovated	1971/1995
Depreciable Lives (Years)	-1	[2]
University Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	University Place
Type	Office
Location	Cambridge, MA
Encumbrances	15,000,000
Original Land	0
Original Building	37,091,000
Costs Capitalized Subsequent to Acquisition	6,785,000
Land and improvements	390,000
Buildings and Improvements	43,486,000
Land Held for Development	0
Total	43,876,000
Accumulated Depreciation	19,225,000
Year(s) built / renovated	1985
Depreciable Lives (Years)	-1	[2]
2600 Tower Oaks Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	2600 Tower Oaks Boulevard
Type	Office
Location	Rockville, MD
Encumbrances	0
Original Land	4,243,000
Original Building	31,125,000
Costs Capitalized Subsequent to Acquisition	7,676,000
Land and improvements	4,785,000
Buildings and Improvements	38,259,000
Land Held for Development	0
Total	43,044,000
Accumulated Depreciation	15,306,000
Year(s) built / renovated	2001
Depreciable Lives (Years)	-1	[2]
Quorum Office Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Quorum Office Park
Type	Office
Location	Chelmsford, MA
Encumbrances	0
Original Land	3,750,000
Original Building	32,454,000
Costs Capitalized Subsequent to Acquisition	5,273,000
Land and improvements	5,187,000
Buildings and Improvements	36,290,000
Land Held for Development	0
Total	41,477,000
Accumulated Depreciation	11,890,000
Year(s) built / renovated	2001
Depreciable Lives (Years)	-1	[2]
One Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	One Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	134,000
Original Building	25,110,000
Costs Capitalized Subsequent to Acquisition	14,982,000
Land and improvements	548,000
Buildings and Improvements	39,678,000
Land Held for Development	0
Total	40,226,000
Accumulated Depreciation	22,594,000
Year(s) built / renovated	1987
Depreciable Lives (Years)	-1	[2]
Three Patriots Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Three Patriots Park (formerly known as 12290 Sunrise Valley Drive)
Type	Office
Location	Reston, VA
Encumbrances	0
Original Land	3,594,000
Original Building	32,977,000
Costs Capitalized Subsequent to Acquisition	1,374,000
Land and improvements	4,009,000
Buildings and Improvements	33,936,000
Land Held for Development	0
Total	37,945,000
Accumulated Depreciation	11,798,000
Year(s) built / renovated	2006
Depreciable Lives (Years)	-1	[2]
500 E Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	500 E Street
Type	Office
Location	Washington, DC
Encumbrances	0
Original Land	109,000
Original Building	22,420,000
Costs Capitalized Subsequent to Acquisition	12,418,000
Land and improvements	2,379,000
Buildings and Improvements	32,568,000
Land Held for Development	0
Total	34,947,000
Accumulated Depreciation	19,595,000
Year(s) built / renovated	1987
Depreciable Lives (Years)	-1	[2]
Eight Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Eight Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	850,000
Original Building	25,042,000
Costs Capitalized Subsequent to Acquisition	8,507,000
Land and improvements	1,323,000
Buildings and Improvements	33,076,000
Land Held for Development	0
Total	34,399,000
Accumulated Depreciation	9,673,000
Year(s) built / renovated	1999
Depreciable Lives (Years)	-1	[2]
10 and 20 Burlington Mall Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	10 and 20 Burlington Mall Road
Type	Office
Location	Burlington, MA
Encumbrances	0
Original Land	930,000
Original Building	6,928,000
Costs Capitalized Subsequent to Acquisition	13,806,000
Land and improvements	802,000
Buildings and Improvements	20,862,000
Land Held for Development	0
Total	21,664,000
Accumulated Depreciation	13,534,000
Year(s) built / renovated	1984-1989/1996
Depreciable Lives (Years)	-1	[2]
Ten Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Ten Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	1,299,000
Original Building	12,943,000
Costs Capitalized Subsequent to Acquisition	6,109,000
Land and improvements	2,395,000
Buildings and Improvements	17,956,000
Land Held for Development	0
Total	20,351,000
Accumulated Depreciation	10,729,000
Year(s) built / renovated	1990
Depreciable Lives (Years)	-1	[2]
Three Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Three Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	174,000
Original Building	12,200,000
Costs Capitalized Subsequent to Acquisition	5,855,000
Land and improvements	367,000
Buildings and Improvements	17,862,000
Land Held for Development	0
Total	18,229,000
Accumulated Depreciation	9,315,000
Year(s) built / renovated	1987
Depreciable Lives (Years)	-1	[2]
201 Spring Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	201 Spring Street
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	2,849,000
Original Building	15,303,000
Costs Capitalized Subsequent to Acquisition	(154,000)
Land and improvements	3,124,000
Buildings and Improvements	14,874,000
Land Held for Development	0
Total	17,998,000
Accumulated Depreciation	5,558,000
Year(s) built / renovated	1997
Depreciable Lives (Years)	-1	[2]
Montvale Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Montvale Center
Type	Office
Location	Gaithersburg, MD
Encumbrances	25,000,000
Original Land	1,574,000
Original Building	9,786,000
Costs Capitalized Subsequent to Acquisition	6,558,000
Land and improvements	2,555,000
Buildings and Improvements	15,363,000
Land Held for Development	0
Total	17,918,000
Accumulated Depreciation	10,307,000
Year(s) built / renovated	1987
Depreciable Lives (Years)	-1	[2]
40 Shattuck Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	40 Shattuck Road
Type	Office
Location	Andover, MA
Encumbrances	0
Original Land	709,000
Original Building	14,740,000
Costs Capitalized Subsequent to Acquisition	2,268,000
Land and improvements	893,000
Buildings and Improvements	16,824,000
Land Held for Development	0
Total	17,717,000
Accumulated Depreciation	4,928,000
Year(s) built / renovated	2001
Depreciable Lives (Years)	-1	[2]
Lexington Office Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Lexington Office Park
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	998,000
Original Building	1,426,000
Costs Capitalized Subsequent to Acquisition	13,503,000
Land and improvements	1,264,000
Buildings and Improvements	14,663,000
Land Held for Development	0
Total	15,927,000
Accumulated Depreciation	9,714,000
Year(s) built / renovated	1982
Depreciable Lives (Years)	-1	[2]
92 - 100 Hayden Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	92-100 Hayden Avenue
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	594,000
Original Building	6,748,000
Costs Capitalized Subsequent to Acquisition	7,819,000
Land and improvements	802,000
Buildings and Improvements	14,359,000
Land Held for Development	0
Total	15,161,000
Accumulated Depreciation	9,160,000
Year(s) built / renovated	1985
Depreciable Lives (Years)	-1	[2]
6601 and 6605 Springfield Center Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	6601 & 6605 Springfield Center Drive
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	14,041,000
Original Building	2,375,000
Costs Capitalized Subsequent to Acquisition	(1,836,000)
Land and improvements	3,777,000
Buildings and Improvements	714,000
Land Held for Development	10,089,000
Total	14,580,000
Accumulated Depreciation	714,000
Year(s) built / renovated	1990
181 Spring Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	181 Spring Street
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	1,066,000
Original Building	9,520,000
Costs Capitalized Subsequent to Acquisition	1,950,000
Land and improvements	1,160,000
Buildings and Improvements	11,376,000
Land Held for Development	0
Total	12,536,000
Accumulated Depreciation	3,704,000
Year(s) built / renovated	1999
Depreciable Lives (Years)	-1	[2]
195 West Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	195 West Street
Type	Office
Location	Waltham, MA
Encumbrances	0
Original Land	1,611,000
Original Building	6,652,000
Costs Capitalized Subsequent to Acquisition	4,175,000
Land and improvements	1,858,000
Buildings and Improvements	10,580,000
Land Held for Development	0
Total	12,438,000
Accumulated Depreciation	5,749,000
Year(s) built / renovated	1990
Depreciable Lives (Years)	-1	[2]
91 Hartwell Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	91 Hartwell Avenue
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	784,000
Original Building	6,464,000
Costs Capitalized Subsequent to Acquisition	4,706,000
Land and improvements	941,000
Buildings and Improvements	11,013,000
Land Held for Development	0
Total	11,954,000
Accumulated Depreciation	7,069,000
Year(s) built / renovated	1985
Depreciable Lives (Years)	-1	[2]
Waltham Office Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Waltham Office Center
Type	Office
Location	Waltham, MA
Encumbrances	0
Original Land	422,000
Original Building	2,719,000
Costs Capitalized Subsequent to Acquisition	9,266,000
Land and improvements	165,000
Buildings and Improvements	8,445,000
Land Held for Development	3,797,000
Total	12,407,000
Accumulated Depreciation	8,051,000
Year(s) built / renovated	1968-1970/1988
Depreciable Lives (Years)	-1	[2]
Eleven Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Eleven Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	121,000
Original Building	5,535,000
Costs Capitalized Subsequent to Acquisition	4,975,000
Land and improvements	324,000
Buildings and Improvements	10,307,000
Land Held for Development	0
Total	10,631,000
Accumulated Depreciation	6,961,000
Year(s) built / renovated	1984
Depreciable Lives (Years)	-1	[2]
7501 Boston Boulevard, Building Seven [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7501 Boston Boulevard, Building Seven
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	665,000
Original Building	9,273,000
Costs Capitalized Subsequent to Acquisition	544,000
Land and improvements	791,000
Buildings and Improvements	9,691,000
Land Held for Development	0
Total	10,482,000
Accumulated Depreciation	3,653,000
Year(s) built / renovated	1997
Depreciable Lives (Years)	-1	[2]
33 Hayden Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	33 Hayden Avenue
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	266,000
Original Building	3,234,000
Costs Capitalized Subsequent to Acquisition	6,073,000
Land and improvements	425,000
Buildings and Improvements	9,148,000
Land Held for Development	0
Total	9,573,000
Accumulated Depreciation	7,011,000
Year(s) built / renovated	1979
Depreciable Lives (Years)	-1	[2]
7435 Boston Boulevard, Building One [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7435 Boston Boulevard, Building One
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	392,000
Original Building	3,822,000
Costs Capitalized Subsequent to Acquisition	3,894,000
Land and improvements	659,000
Buildings and Improvements	7,449,000
Land Held for Development	0
Total	8,108,000
Accumulated Depreciation	5,144,000
Year(s) built / renovated	1982
Depreciable Lives (Years)	-1	[2]
7450 Boston Boulevard, Building Three [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7450 Boston Boulevard, Building Three
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	1,165,000
Original Building	4,681,000
Costs Capitalized Subsequent to Acquisition	1,915,000
Land and improvements	1,430,000
Buildings and Improvements	6,331,000
Land Held for Development	0
Total	7,761,000
Accumulated Depreciation	2,743,000
Year(s) built / renovated	1987
Depreciable Lives (Years)	-1	[2]
8000 Grainger Court, Building Five [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	8000 Grainger Court, Building Five
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	366,000
Original Building	4,282,000
Costs Capitalized Subsequent to Acquisition	2,944,000
Land and improvements	601,000
Buildings and Improvements	6,991,000
Land Held for Development	0
Total	7,592,000
Accumulated Depreciation	4,840,000
Year(s) built / renovated	1984
Depreciable Lives (Years)	-1	[2]
453 Ravendale Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	453 Ravendale Drive
Type	Office
Location	Mountain View, CA
Encumbrances	0
Original Land	5,477,000
Original Building	1,090,000
Costs Capitalized Subsequent to Acquisition	172,000
Land and improvements	5,477,000
Buildings and Improvements	1,262,000
Land Held for Development	0
Total	6,739,000
Accumulated Depreciation	67,000
Year(s) built / renovated	1977
Depreciable Lives (Years)	-1	[2]
7500 Boston Boulevard, Building Six [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7500 Boston Boulevard, Building Six
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	138,000
Original Building	3,749,000
Costs Capitalized Subsequent to Acquisition	2,597,000
Land and improvements	406,000
Buildings and Improvements	6,078,000
Land Held for Development	0
Total	6,484,000
Accumulated Depreciation	3,945,000
Year(s) built / renovated	1985
Depreciable Lives (Years)	-1	[2]
7601 Boston Boulevard, Building Eight [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7601 Boston Boulevard, Building Eight
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	200,000
Original Building	878,000
Costs Capitalized Subsequent to Acquisition	4,875,000
Land and improvements	551,000
Buildings and Improvements	5,402,000
Land Held for Development	0
Total	5,953,000
Accumulated Depreciation	3,415,000
Year(s) built / renovated	1986
Depreciable Lives (Years)	-1	[2]
Fourteen Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Fourteen Cambridge Center
Type	Office
Location	Cambridge, MA
Encumbrances	0
Original Land	110,000
Original Building	4,483,000
Costs Capitalized Subsequent to Acquisition	1,223,000
Land and improvements	273,000
Buildings and Improvements	5,543,000
Land Held for Development	0
Total	5,816,000
Accumulated Depreciation	3,667,000
Year(s) built / renovated	1983
Depreciable Lives (Years)	-1	[2]
7300 Boston Boulevard, Building Thirteen [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7300 Boston Boulevard, Building Thirteen
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	608,000
Original Building	4,773,000
Costs Capitalized Subsequent to Acquisition	230,000
Land and improvements	661,000
Buildings and Improvements	4,950,000
Land Held for Development	0
Total	5,611,000
Accumulated Depreciation	3,580,000
Year(s) built / renovated	2002
Depreciable Lives (Years)	-1	[2]
8000 Corporate Court, Building Eleven [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	8000 Corporate Court, Building Eleven
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	136,000
Original Building	3,071,000
Costs Capitalized Subsequent to Acquisition	1,484,000
Land and improvements	775,000
Buildings and Improvements	3,916,000
Land Held for Development	0
Total	4,691,000
Accumulated Depreciation	2,222,000
Year(s) built / renovated	1989
Depreciable Lives (Years)	-1	[2]
7374 Boston Boulevard, Building Four [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7374 Boston Boulevard, Building Four
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	241,000
Original Building	1,605,000
Costs Capitalized Subsequent to Acquisition	1,899,000
Land and improvements	398,000
Buildings and Improvements	3,347,000
Land Held for Development	0
Total	3,745,000
Accumulated Depreciation	2,220,000
Year(s) built / renovated	1984
Depreciable Lives (Years)	-1	[2]
7375 Boston Boulevard, Building Ten [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7375 Boston Boulevard, Building Ten
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	23,000
Original Building	2,685,000
Costs Capitalized Subsequent to Acquisition	1,007,000
Land and improvements	93,000
Buildings and Improvements	3,622,000
Land Held for Development	0
Total	3,715,000
Accumulated Depreciation	2,156,000
Year(s) built / renovated	1988
Depreciable Lives (Years)	-1	[2]
7451 Boston Boulevard, Building Two [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	7451 Boston Boulevard, Building Two
Type	Office
Location	Springfield, VA
Encumbrances	0
Original Land	249,000
Original Building	1,542,000
Costs Capitalized Subsequent to Acquisition	1,313,000
Land and improvements	613,000
Buildings and Improvements	2,491,000
Land Held for Development	0
Total	3,104,000
Accumulated Depreciation	2,074,000
Year(s) built / renovated	1982
Depreciable Lives (Years)	-1	[2]
32 Hartwell Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	32 Hartwell Avenue
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	168,000
Original Building	1,943,000
Costs Capitalized Subsequent to Acquisition	440,000
Land and improvements	314,000
Buildings and Improvements	2,237,000
Land Held for Development	0
Total	2,551,000
Accumulated Depreciation	1,438,000
Year(s) built / renovated	1968-1979/1987
Depreciable Lives (Years)	-1	[2]
164 Lexington Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	164 Lexington Road
Type	Office
Location	Billerica, MA
Encumbrances	0
Original Land	592,000
Original Building	1,370,000
Costs Capitalized Subsequent to Acquisition	319,000
Land and improvements	643,000
Buildings and Improvements	1,638,000
Land Held for Development	0
Total	2,281,000
Accumulated Depreciation	662,000
Year(s) built / renovated	1982
Depreciable Lives (Years)	-1	[2]
Seventeen Hartwell Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	17 Hartwell Avenue
Type	Office
Location	Lexington, MA
Encumbrances	0
Original Land	26,000
Original Building	150,000
Costs Capitalized Subsequent to Acquisition	1,002,000
Land and improvements	65,000
Buildings and Improvements	1,113,000
Land Held for Development	0
Total	1,178,000
Accumulated Depreciation	563,000
Year(s) built / renovated	1968
Depreciable Lives (Years)	-1	[2]
Residences on The Avenue, Two Two Two One I St., NW [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Residences on The Avenue, 2221 I St., NW
Type	Residential
Location	Washington, DC
Encumbrances	0
Original Land	0
Original Building	119,874,000
Costs Capitalized Subsequent to Acquisition	(39,000)
Land and improvements	0
Buildings and Improvements	119,835,000
Land Held for Development	0
Total	119,835,000
Accumulated Depreciation	4,857,000
Year(s) built / renovated	2011
Depreciable Lives (Years)	-1	[2]
The Lofts At Atlantic Wharf [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	The Lofts at Atlantic Wharf
Type	Residential
Location	Boston, MA
Encumbrances	0
Original Land	3,529,000
Original Building	54,891,000
Costs Capitalized Subsequent to Acquisition	971,000
Land and improvements	3,529,000
Buildings and Improvements	55,862,000
Land Held for Development	0
Total	59,391,000
Accumulated Depreciation	2,111,000
Year(s) built / renovated	2011
Depreciable Lives (Years)	-1	[2]
Cambridge Center Marriott [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Cambridge Center Marriott
Type	Hotel
Location	Cambridge, MA
Encumbrances	0
Original Land	478,000
Original Building	37,918,000
Costs Capitalized Subsequent to Acquisition	34,595,000
Land and improvements	1,201,000
Buildings and Improvements	71,790,000
Land Held for Development	0
Total	72,991,000
Accumulated Depreciation	44,011,000
Year(s) built / renovated	1986
Depreciable Lives (Years)	-1	[2]
Cambridge Center East Garage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Cambridge Center East Garage
Type	Garage
Location	Cambridge, MA
Encumbrances	0
Original Land	0
Original Building	35,035,000
Costs Capitalized Subsequent to Acquisition	1,487,000
Land and improvements	103,000
Buildings and Improvements	36,419,000
Land Held for Development	0
Total	36,522,000
Accumulated Depreciation	5,721,000
Year(s) built / renovated	1984
Depreciable Lives (Years)	-1	[2]
Cambridge Center West Garage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Cambridge Center West Garage
Type	Garage
Location	Cambridge, MA
Encumbrances	0
Original Land	1,256,000
Original Building	15,697,000
Costs Capitalized Subsequent to Acquisition	1,221,000
Land and improvements	1,434,000
Buildings and Improvements	16,740,000
Land Held for Development	0
Total	18,174,000
Accumulated Depreciation	2,951,000
Year(s) built / renovated	2006
Depreciable Lives (Years)	-1	[2]
Cambridge Center North Garage [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Cambridge Center North Garage
Type	Garage
Location	Cambridge, MA
Encumbrances	0
Original Land	1,163,000
Original Building	11,633,000
Costs Capitalized Subsequent to Acquisition	2,750,000
Land and improvements	1,579,000
Buildings and Improvements	13,967,000
Land Held for Development	0
Total	15,546,000
Accumulated Depreciation	7,745,000
Year(s) built / renovated	1990
Depreciable Lives (Years)	-1	[2]
250 West 55th Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	250 West 55th Street
Type	Development
Location	New York, NY
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	714,451,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	0
Development and Construction in Progress	714,451,000
Total	714,451,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
680 Folsom Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	680 Folsom Street
Type	Development
Location	San Francisco, CA
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	147,815,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	3,058,000
Development and Construction in Progress	144,757,000
Total	147,815,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Two Patriots Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Two Patriots Park (formerly known as 12300 Sunrise Valley Drive)
Type	Development
Location	Reston, VA
Original Land	9,062,000
Original Building	58,884,000
Costs Capitalized Subsequent to Acquisition	54,309,000
Land and improvements	11,009,000
Buildings and Improvements	65,426,000
Land Held for Development	0
Development and Construction in Progress	45,820,000
Total	122,255,000
Accumulated Depreciation	43,278,000
Year(s) built / renovated	1987/1988
Depreciable Lives (Years)	N/A
The Avant at Reston Town Center Residential [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	The Avant at Reston Town Center Residential
Type	Development
Location	Reston, VA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	67,548,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	0
Development and Construction in Progress	67,548,000
Total	67,548,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Seventeen Cambridge Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	17 Cambridge Center
Type	Development
Location	Cambridge, MA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	55,264,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	0
Development and Construction in Progress	55,264,000
Total	55,264,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Plaza at Almaden [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Plaza at Almaden
Type	Land
Location	San Jose, CA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	37,306,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	37,306,000
Development and Construction in Progress	0
Total	37,306,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Springfield Metro Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Springfield Metro Center
Type	Land
Location	Springfield, VA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	31,965,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	31,965,000
Development and Construction in Progress	0
Total	31,965,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Tower Oaks Master Plan [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Tower Oaks Master Plan
Type	Land
Location	Rockville, MD
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	28,624,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	28,624,000
Development and Construction in Progress	0
Total	28,624,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Prospect Hill [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Prospect Hill
Type	Land
Location	Waltham, MA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	23,800,000
Land and improvements	0
Buildings and Improvements	667,000
Land Held for Development	23,133,000
Development and Construction in Progress	0
Total	23,800,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Washingtonian North [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Washingtonian North
Type	Land
Location	Gaithersburg, MD
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	17,891,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	17,891,000
Development and Construction in Progress	0
Total	17,891,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
103 4th Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	103 4th Avenue
Type	Land
Location	Waltham, MA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	11,911,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	11,911,000
Development and Construction in Progress	0
Total	11,911,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Cambridge Master Plan [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Cambridge Master Plan
Type	Land
Location	Cambridge, MA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	10,896,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	10,896,000
Development and Construction in Progress	0
Total	10,896,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Reston Gateway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Reston Gateway
Type	Land
Location	Reston, VA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	9,521,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	9,521,000
Development and Construction in Progress	0
Total	9,521,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Reston Eastgate [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Reston Eastgate
Type	Land
Location	Reston, VA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	8,801,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	8,801,000
Development and Construction in Progress	0
Total	8,801,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Crane Meadow [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Crane Meadow
Type	Land
Location	Marlborough, MA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	8,725,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	8,725,000
Development and Construction in Progress	0
Total	8,725,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Broad Run Business Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	Broad Run Business Park
Type	Land
Location	Loudon County, VA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	7,851,000
Land and improvements	1,621,000
Buildings and Improvements	0
Land Held for Development	6,230,000
Development and Construction in Progress	0
Total	7,851,000
Accumulated Depreciation	0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
30 Shattuck Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property Name	30 Shattuck Road
Type	Land
Location	Andover, MA
Encumbrances	0
Original Land	0
Original Building	0
Costs Capitalized Subsequent to Acquisition	1,190,000
Land and improvements	0
Buildings and Improvements	0
Land Held for Development	1,190,000
Development and Construction in Progress	0
Total	1,190,000
Accumulated Depreciation	$ 0
Year(s) built / renovated	N/A
Depreciable Lives (Years)	N/A
Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Life Used for Depreciation	life of the lease

[1] (2)Includes the unamortized balance of the historical fair value adjustment totaling approximately $38.6 million.

[2] (1)Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.