Schedule III - Real Estate and Accumulated Deprecation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				$ 2,035,959
Land and Improvements				1,340,744
Buildings and Improvements				2,922,442
Costs Capitalized Subsequent to Acquisition(2)				1,762,611
Land and Improvements				1,376,587
Buildings and Improvements				4,649,210
Total	$ 4,155,391	$ 4,038,206	$ 3,809,213	6,025,797
Accumulated Depreciation and Amortization	930,769	908,233	797,806	1,011,330
Cost of real estate for federal income tax purposes				3,500,000
Real Estate:
Balance at beginning of the year	4,155,391	4,038,206	3,809,213
Land and improvements	428,702	0	0
Buildings and improvements	1,489,409	217,261	252,113
Held for sale	8,293	0	0
Less: Assets written‑off	(55,998)	(100,076)	(23,120)
Balance at end of the year	6,025,797	4,155,391	4,038,206
Accumulated Depreciation:
Balance at beginning of period	930,769	908,233	797,806
Additions charged to operating expenses	136,559	122,612	133,582
Less: Accumulated depreciation on assets written‑off	(55,998)	(100,076)	(23,155)
Balance at end of period	1,011,330	$ 930,769	$ 908,233
Universal Buildings
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				184,357
Land and Improvements				69,393
Buildings and Improvements				143,320
Costs Capitalized Subsequent to Acquisition(2)				22,547
Land and Improvements				68,612
Buildings and Improvements				166,648
Total	235,260			235,260
Accumulated Depreciation and Amortization	48,187			48,187
Real Estate:
Balance at end of the year	235,260
Accumulated Depreciation:
Balance at end of period	48,187
2101 L Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				140,493
Land and Improvements				32,815
Buildings and Improvements				51,642
Costs Capitalized Subsequent to Acquisition(2)				83,766
Land and Improvements				39,768
Buildings and Improvements				128,455
Total	168,223			168,223
Accumulated Depreciation and Amortization	40,822			40,822
Real Estate:
Balance at end of the year	168,223
Accumulated Depreciation:
Balance at end of period	40,822
Bowen Building
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				30,077
Buildings and Improvements				98,962
Costs Capitalized Subsequent to Acquisition(2)				6,238
Land and Improvements				30,176
Buildings and Improvements				105,101
Total	135,277			135,277
Accumulated Depreciation and Amortization	32,854			32,854
Real Estate:
Balance at end of the year	135,277
Accumulated Depreciation:
Balance at end of period	32,854
1730 M Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				10,095
Buildings and Improvements				17,541
Costs Capitalized Subsequent to Acquisition(2)				16,111
Land and Improvements				10,687
Buildings and Improvements				33,060
Total	43,747			43,747
Accumulated Depreciation and Amortization	12,537			12,537
Real Estate:
Balance at end of the year	43,747
Accumulated Depreciation:
Balance at end of period	12,537
1233 20th Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				42,684
Land and Improvements				30,505
Buildings and Improvements				23,130
Costs Capitalized Subsequent to Acquisition(2)				338
Land and Improvements				30,505
Buildings and Improvements				23,468
Total	53,973			53,973
Accumulated Depreciation and Amortization	735			735
Real Estate:
Balance at end of the year	53,973
Accumulated Depreciation:
Balance at end of period	735
Executive Tower
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				33,481
Buildings and Improvements				67,363
Costs Capitalized Subsequent to Acquisition(2)				9,306
Land and Improvements				34,178
Buildings and Improvements				75,972
Total	110,150			110,150
Accumulated Depreciation and Amortization	13,180			13,180
Real Estate:
Balance at end of the year	110,150
Accumulated Depreciation:
Balance at end of period	13,180
1600 K Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				19,870
Buildings and Improvements				10,308
Costs Capitalized Subsequent to Acquisition(2)				193
Land and Improvements				19,870
Buildings and Improvements				10,501
Total	30,371			30,371
Accumulated Depreciation and Amortization	402			402
Real Estate:
Balance at end of the year	30,371
Accumulated Depreciation:
Balance at end of period	402
Courthouse Plaza 1 and 2
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				2,000
Land and Improvements				0
Buildings and Improvements				105,475
Costs Capitalized Subsequent to Acquisition(2)				56,173
Land and Improvements				0
Buildings and Improvements				161,648
Total	161,648			161,648
Accumulated Depreciation and Amortization	67,974			67,974
Real Estate:
Balance at end of the year	161,648
Accumulated Depreciation:
Balance at end of period	67,974
2345 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				23,126
Buildings and Improvements				93,918
Costs Capitalized Subsequent to Acquisition(2)				35,612
Land and Improvements				23,546
Buildings and Improvements				129,110
Total	152,656			152,656
Accumulated Depreciation and Amortization	54,253			54,253
Real Estate:
Balance at end of the year	152,656
Accumulated Depreciation:
Balance at end of period	54,253
2121 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				139,134
Land and Improvements				21,503
Buildings and Improvements				87,329
Costs Capitalized Subsequent to Acquisition(2)				47,790
Land and Improvements				21,934
Buildings and Improvements				134,688
Total	156,622			156,622
Accumulated Depreciation and Amortization	65,256			65,256
Real Estate:
Balance at end of the year	156,622
Accumulated Depreciation:
Balance at end of period	65,256
1550 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				22,182
Buildings and Improvements				70,525
Costs Capitalized Subsequent to Acquisition(2)				19,796
Land and Improvements				21,585
Buildings and Improvements				90,918
Total	112,503			112,503
Accumulated Depreciation and Amortization	37,886			37,886
Real Estate:
Balance at end of the year	112,503
Accumulated Depreciation:
Balance at end of period	37,886
RTC - West
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				107,720
Land and Improvements				30,326
Buildings and Improvements				134,108
Costs Capitalized Subsequent to Acquisition(2)				(110)
Land and Improvements				30,397
Buildings and Improvements				133,927
Total	164,324			164,324
Accumulated Depreciation and Amortization	3,330			3,330
Real Estate:
Balance at end of the year	164,324
Accumulated Depreciation:
Balance at end of period	3,330
2231 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				20,611
Buildings and Improvements				83,705
Costs Capitalized Subsequent to Acquisition(2)				18,856
Land and Improvements				21,001
Buildings and Improvements				102,171
Total	123,172			123,172
Accumulated Depreciation and Amortization	38,807			38,807
Real Estate:
Balance at end of the year	123,172
Accumulated Depreciation:
Balance at end of period	38,807
2011 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				18,940
Buildings and Improvements				76,921
Costs Capitalized Subsequent to Acquisition(2)				33,139
Land and Improvements				18,871
Buildings and Improvements				110,129
Total	129,000			129,000
Accumulated Depreciation and Amortization	45,263			45,263
Real Estate:
Balance at end of the year	129,000
Accumulated Depreciation:
Balance at end of period	45,263
2451 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				16,755
Buildings and Improvements				68,047
Costs Capitalized Subsequent to Acquisition(2)				27,307
Land and Improvements				17,090
Buildings and Improvements				95,019
Total	112,109			112,109
Accumulated Depreciation and Amortization	35,934			35,934
Real Estate:
Balance at end of the year	112,109
Accumulated Depreciation:
Balance at end of period	35,934
Commerce Executive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				13,401
Buildings and Improvements				58,705
Costs Capitalized Subsequent to Acquisition(2)				26,122
Land and Improvements				13,140
Buildings and Improvements				85,088
Total	98,228			98,228
Accumulated Depreciation and Amortization	33,829			33,829
Real Estate:
Balance at end of the year	98,228
Accumulated Depreciation:
Balance at end of period	33,829
1235 S. Clark Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				78,000
Land and Improvements				15,826
Buildings and Improvements				56,090
Costs Capitalized Subsequent to Acquisition(2)				27,075
Land and Improvements				16,189
Buildings and Improvements				82,802
Total	98,991			98,991
Accumulated Depreciation and Amortization	30,358			30,358
Real Estate:
Balance at end of the year	98,991
Accumulated Depreciation:
Balance at end of period	30,358
241 18th Street S.
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				13,867
Buildings and Improvements				54,169
Costs Capitalized Subsequent to Acquisition(2)				25,164
Land and Improvements				14,894
Buildings and Improvements				78,306
Total	93,200			93,200
Accumulated Depreciation and Amortization	30,915			30,915
Real Estate:
Balance at end of the year	93,200
Accumulated Depreciation:
Balance at end of period	30,915
251 18th Street S.
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				35,792
Land and Improvements				12,305
Buildings and Improvements				49,360
Costs Capitalized Subsequent to Acquisition(2)				50,928
Land and Improvements				12,809
Buildings and Improvements				99,784
Total	112,593			112,593
Accumulated Depreciation and Amortization	34,678			34,678
Real Estate:
Balance at end of the year	112,593
Accumulated Depreciation:
Balance at end of period	34,678
1215 S. Clark Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				34,299
Land and Improvements				13,636
Buildings and Improvements				48,380
Costs Capitalized Subsequent to Acquisition(2)				54,196
Land and Improvements				13,926
Buildings and Improvements				102,286
Total	116,212			116,212
Accumulated Depreciation and Amortization	27,373			27,373
Real Estate:
Balance at end of the year	116,212
Accumulated Depreciation:
Balance at end of period	27,373
201 12th Street S.
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				14,766
Buildings and Improvements				52,750
Costs Capitalized Subsequent to Acquisition(2)				22,680
Land and Improvements				15,036
Buildings and Improvements				75,160
Total	90,196			90,196
Accumulated Depreciation and Amortization	27,838			27,838
Real Estate:
Balance at end of the year	90,196
Accumulated Depreciation:
Balance at end of period	27,838
800 North Glebe Road
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				107,500
Land and Improvements				28,168
Buildings and Improvements				140,983
Costs Capitalized Subsequent to Acquisition(2)				2,182
Land and Improvements				28,168
Buildings and Improvements				143,165
Total	171,333			171,333
Accumulated Depreciation and Amortization	2,737			2,737
Real Estate:
Balance at end of the year	171,333
Accumulated Depreciation:
Balance at end of period	2,737
1225 S. Clark Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				11,176
Buildings and Improvements				43,495
Costs Capitalized Subsequent to Acquisition(2)				19,649
Land and Improvements				11,413
Buildings and Improvements				62,907
Total	74,320			74,320
Accumulated Depreciation and Amortization	23,247			23,247
Real Estate:
Balance at end of the year	74,320
Accumulated Depreciation:
Balance at end of period	23,247
2200 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				13,104
Buildings and Improvements				30,050
Costs Capitalized Subsequent to Acquisition(2)				32,798
Land and Improvements				13,378
Buildings and Improvements				62,574
Total	75,952			75,952
Accumulated Depreciation and Amortization	18,075			18,075
Real Estate:
Balance at end of the year	75,952
Accumulated Depreciation:
Balance at end of period	18,075
1901 South Bell Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				11,669
Buildings and Improvements				36,918
Costs Capitalized Subsequent to Acquisition(2)				22,584
Land and Improvements				11,669
Buildings and Improvements				59,502
Total	71,171			71,171
Accumulated Depreciation and Amortization	24,931			24,931
Real Estate:
Balance at end of the year	71,171
Accumulated Depreciation:
Balance at end of period	24,931
2100 Crystal Drive
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				10,287
Buildings and Improvements				23,590
Costs Capitalized Subsequent to Acquisition(2)				31,712
Land and Improvements				10,520
Buildings and Improvements				55,069
Total	65,589			65,589
Accumulated Depreciation and Amortization	22,490			22,490
Real Estate:
Balance at end of the year	65,589
Accumulated Depreciation:
Balance at end of period	22,490
200 12th Street S.
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				17,227
Land and Improvements				8,016
Buildings and Improvements				30,552
Costs Capitalized Subsequent to Acquisition(2)				19,423
Land and Improvements				8,186
Buildings and Improvements				49,805
Total	57,991			57,991
Accumulated Depreciation and Amortization	18,490			18,490
Real Estate:
Balance at end of the year	57,991
Accumulated Depreciation:
Balance at end of period	18,490
2001 Jefferson Davis Highway
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				7,300
Buildings and Improvements				16,746
Costs Capitalized Subsequent to Acquisition(2)				11,297
Land and Improvements				7,281
Buildings and Improvements				28,062
Total	35,343			35,343
Accumulated Depreciation and Amortization	10,135			10,135
Real Estate:
Balance at end of the year	35,343
Accumulated Depreciation:
Balance at end of period	10,135
Summit I
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				29,500
Land and Improvements				7,317
Buildings and Improvements				30,626
Costs Capitalized Subsequent to Acquisition(2)				379
Land and Improvements				7,317
Buildings and Improvements				31,005
Total	38,322			38,322
Accumulated Depreciation and Amortization	662			662
Real Estate:
Balance at end of the year	38,322
Accumulated Depreciation:
Balance at end of period	662
Summit II
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				29,500
Land and Improvements				5,535
Buildings and Improvements				28,463
Costs Capitalized Subsequent to Acquisition(2)				332
Land and Improvements				5,535
Buildings and Improvements				28,795
Total	34,330			34,330
Accumulated Depreciation and Amortization	741			741
Real Estate:
Balance at end of the year	34,330
Accumulated Depreciation:
Balance at end of period	741
1800 South Bell Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				28,702
Costs Capitalized Subsequent to Acquisition(2)				7,220
Land and Improvements				0
Buildings and Improvements				35,922
Total	35,922			35,922
Accumulated Depreciation and Amortization	14,835			14,835
Real Estate:
Balance at end of the year	35,922
Accumulated Depreciation:
Balance at end of period	14,835
Crystal City Shops at 2100
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				4,059
Buildings and Improvements				9,309
Costs Capitalized Subsequent to Acquisition(2)				5,229
Land and Improvements				4,049
Buildings and Improvements				14,548
Total	18,597			18,597
Accumulated Depreciation and Amortization	5,611			5,611
Real Estate:
Balance at end of the year	18,597
Accumulated Depreciation:
Balance at end of period	5,611
Wiehle Avenue Office Building
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				96
Costs Capitalized Subsequent to Acquisition(2)				0
Land and Improvements				0
Buildings and Improvements				96
Total	96			96
Accumulated Depreciation and Amortization	48			48
Real Estate:
Balance at end of the year	96
Accumulated Depreciation:
Balance at end of period	48
1831 Wiehle Avenue
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				24
Land and Improvements				0
Buildings and Improvements				24
Total	24			24
Accumulated Depreciation and Amortization	2			2
Real Estate:
Balance at end of the year	24
Accumulated Depreciation:
Balance at end of period	2
Crystal Drive Retail
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				20,465
Costs Capitalized Subsequent to Acquisition(2)				6,034
Land and Improvements				55
Buildings and Improvements				26,444
Total	26,499			26,499
Accumulated Depreciation and Amortization	12,133			12,133
Real Estate:
Balance at end of the year	26,499
Accumulated Depreciation:
Balance at end of period	12,133
7200 Wisconsin Avenue
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				83,130
Land and Improvements				34,683
Buildings and Improvements				92,059
Costs Capitalized Subsequent to Acquisition(2)				885
Land and Improvements				34,683
Buildings and Improvements				92,944
Total	127,627			127,627
Accumulated Depreciation and Amortization	1,763			1,763
Real Estate:
Balance at end of the year	127,627
Accumulated Depreciation:
Balance at end of period	1,763
One Democracy Plaza
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				33,628
Costs Capitalized Subsequent to Acquisition(2)				6,572
Land and Improvements				0
Buildings and Improvements				40,200
Total	40,200			40,200
Accumulated Depreciation and Amortization	21,915			21,915
Real Estate:
Balance at end of the year	40,200
Accumulated Depreciation:
Balance at end of period	21,915
4749 Bethesda Avenue Retail
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				11,830
Costs Capitalized Subsequent to Acquisition(2)				2,664
Land and Improvements				0
Buildings and Improvements				14,494
Total	14,494			14,494
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	14,494
Accumulated Depreciation:
Balance at end of period	0
RTC - West Retail
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				2,894
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				7,011
Land and Improvements				2,894
Buildings and Improvements				7,011
Total	9,905			9,905
Accumulated Depreciation and Amortization	103			103
Real Estate:
Balance at end of the year	9,905
Accumulated Depreciation:
Balance at end of period	103
1900 N Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				8,865
Costs Capitalized Subsequent to Acquisition(2)				86,336
Land and Improvements				0
Buildings and Improvements				95,201
Total	95,201			95,201
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	95,201
Accumulated Depreciation:
Balance at end of period	0
CEB Tower at Central Place
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				178,783
Land and Improvements				0
Buildings and Improvements				230,280
Costs Capitalized Subsequent to Acquisition(2)				117,898
Land and Improvements				0
Buildings and Improvements				348,178
Total	348,178			348,178
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	348,178
Accumulated Depreciation:
Balance at end of period	0
4747 Bethesda Avenue
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				10,040
Costs Capitalized Subsequent to Acquisition(2)				46,782
Land and Improvements				0
Buildings and Improvements				56,822
Total	56,822			56,822
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	56,822
Accumulated Depreciation:
Balance at end of period	0
Fort Totten Square
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				73,600
Land and Improvements				24,390
Buildings and Improvements				90,404
Costs Capitalized Subsequent to Acquisition(2)				566
Land and Improvements				24,390
Buildings and Improvements				90,970
Total	115,360			115,360
Accumulated Depreciation and Amortization	1,785			1,785
Real Estate:
Balance at end of the year	115,360
Accumulated Depreciation:
Balance at end of period	1,785
WestEnd25
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				99,456
Land and Improvements				67,049
Buildings and Improvements				5,039
Costs Capitalized Subsequent to Acquisition(2)				109,922
Land and Improvements				68,201
Buildings and Improvements				113,809
Total	182,010			182,010
Accumulated Depreciation and Amortization	23,983			23,983
Real Estate:
Balance at end of the year	182,010
Accumulated Depreciation:
Balance at end of period	23,983
RiverHouse Apartments
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				307,710
Land and Improvements				118,421
Buildings and Improvements				125,078
Costs Capitalized Subsequent to Acquisition(2)				82,825
Land and Improvements				138,763
Buildings and Improvements				187,561
Total	326,324			326,324
Accumulated Depreciation and Amortization	56,476			56,476
Real Estate:
Balance at end of the year	326,324
Accumulated Depreciation:
Balance at end of period	56,476
The Bartlett
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				220,000
Land and Improvements				41,687
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				224,805
Land and Improvements				41,687
Buildings and Improvements				224,805
Total	266,492			266,492
Accumulated Depreciation and Amortization	10,074			10,074
Real Estate:
Balance at end of the year	266,492
Accumulated Depreciation:
Balance at end of period	10,074
220 20th Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				8,434
Buildings and Improvements				19,340
Costs Capitalized Subsequent to Acquisition(2)				99,259
Land and Improvements				8,693
Buildings and Improvements				118,340
Total	127,033			127,033
Accumulated Depreciation and Amortization	27,749			27,749
Real Estate:
Balance at end of the year	127,033
Accumulated Depreciation:
Balance at end of period	27,749
2221 South Clark Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				7,405
Buildings and Improvements				16,981
Costs Capitalized Subsequent to Acquisition(2)				41,598
Land and Improvements				7,386
Buildings and Improvements				58,598
Total	65,984			65,984
Accumulated Depreciation and Amortization	4,109			4,109
Real Estate:
Balance at end of the year	65,984
Accumulated Depreciation:
Balance at end of period	4,109
Falkland Chase - South & West
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				41,976
Land and Improvements				18,530
Buildings and Improvements				44,232
Costs Capitalized Subsequent to Acquisition(2)				107
Land and Improvements				18,530
Buildings and Improvements				44,339
Total	62,869			62,869
Accumulated Depreciation and Amortization	910			910
Real Estate:
Balance at end of the year	62,869
Accumulated Depreciation:
Balance at end of period	910
Falkland Chase - North
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				22,566
Land and Improvements				9,810
Buildings and Improvements				22,706
Costs Capitalized Subsequent to Acquisition(2)				6
Land and Improvements				9,810
Buildings and Improvements				22,712
Total	32,522			32,522
Accumulated Depreciation and Amortization	477			477
Real Estate:
Balance at end of the year	32,522
Accumulated Depreciation:
Balance at end of period	477
West Half
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				1,338
Land and Improvements				0
Buildings and Improvements				17,902
Costs Capitalized Subsequent to Acquisition(2)				69,424
Land and Improvements				0
Buildings and Improvements				87,326
Total	87,326			87,326
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	87,326
Accumulated Depreciation:
Balance at end of period	0
965 Florida Avenue
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				22,665
Land and Improvements				0
Buildings and Improvements				22,665
Total	22,665			22,665
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	22,665
Accumulated Depreciation:
Balance at end of period	0
1221 Van Street
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				59,194
Land and Improvements				0
Buildings and Improvements				63,775
Costs Capitalized Subsequent to Acquisition(2)				46,834
Land and Improvements				0
Buildings and Improvements				110,609
Total	110,609			110,609
Accumulated Depreciation and Amortization	1			1
Real Estate:
Balance at end of the year	110,609
Accumulated Depreciation:
Balance at end of period	1
Atlantic Plumbing C
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				13,952
Costs Capitalized Subsequent to Acquisition(2)				63,269
Land and Improvements				0
Buildings and Improvements				77,221
Total	77,221			77,221
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	77,221
Accumulated Depreciation:
Balance at end of period	0
North End Retail
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				5,847
Buildings and Improvements				9,333
Costs Capitalized Subsequent to Acquisition(2)				(107)
Land and Improvements				5,847
Buildings and Improvements				9,226
Total	15,073			15,073
Accumulated Depreciation and Amortization	179			179
Real Estate:
Balance at end of the year	15,073
Accumulated Depreciation:
Balance at end of period	179
Vienna Retail
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				1,763
Buildings and Improvements				641
Costs Capitalized Subsequent to Acquisition(2)				41
Land and Improvements				1,763
Buildings and Improvements				682
Total	2,445			2,445
Accumulated Depreciation and Amortization	213			213
Real Estate:
Balance at end of the year	2,445
Accumulated Depreciation:
Balance at end of period	213
Crystal City Marriott Hotel
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				8,000
Buildings and Improvements				47,191
Costs Capitalized Subsequent to Acquisition(2)				12,595
Land and Improvements				8,224
Buildings and Improvements				59,562
Total	67,786			67,786
Accumulated Depreciation and Amortization	20,529			20,529
Real Estate:
Balance at end of the year	67,786
Accumulated Depreciation:
Balance at end of period	20,529
Metropolitan Park 6-8
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				65,259
Buildings and Improvements				1,326
Costs Capitalized Subsequent to Acquisition(2)				26,574
Land and Improvements				82,898
Buildings and Improvements				10,261
Total	93,159			93,159
Accumulated Depreciation and Amortization	27			27
Real Estate:
Balance at end of the year	93,159
Accumulated Depreciation:
Balance at end of period	27
Pen Place - Land Parcel
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				104,473
Buildings and Improvements				55
Costs Capitalized Subsequent to Acquisition(2)				(32,322)
Land and Improvements				61,970
Buildings and Improvements				10,236
Total	72,206			72,206
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	72,206
Accumulated Depreciation:
Balance at end of period	0
1700 M Street Dev
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				34,178
Buildings and Improvements				46,938
Costs Capitalized Subsequent to Acquisition(2)				(26,487)
Land and Improvements				34,183
Buildings and Improvements				20,446
Total	54,629			54,629
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	54,629
Accumulated Depreciation:
Balance at end of period	0
Capitol Point - North
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				32,730
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				147
Land and Improvements				32,846
Buildings and Improvements				31
Total	32,877			32,877
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	32,877
Accumulated Depreciation:
Balance at end of period	0
Potomac Yard Land Bay G - Parcels A - F
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				20,318
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				132
Land and Improvements				20,318
Buildings and Improvements				132
Total	20,450			20,450
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	20,450
Accumulated Depreciation:
Balance at end of period	0
Square 649
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				15,550
Buildings and Improvements				6,451
Costs Capitalized Subsequent to Acquisition(2)				(2,328)
Land and Improvements				12,803
Buildings and Improvements				6,870
Total	19,673			19,673
Accumulated Depreciation and Amortization	367			367
Real Estate:
Balance at end of the year	19,673
Accumulated Depreciation:
Balance at end of period	367
Other Future Development Assets
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				140,919
Buildings and Improvements				112,653
Costs Capitalized Subsequent to Acquisition(2)				(9,091)
Land and Improvements				170,620
Buildings and Improvements				73,861
Total	244,481			244,481
Accumulated Depreciation and Amortization	62			62
Real Estate:
Balance at end of the year	244,481
Accumulated Depreciation:
Balance at end of period	62
Corporate
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				0
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				21,939
Land and Improvements				0
Buildings and Improvements				21,939
Total	21,939			21,939
Accumulated Depreciation and Amortization	4,060			4,060
Real Estate:
Balance at end of the year	21,939
Accumulated Depreciation:
Balance at end of period	4,060
Properties Not Held For Sale
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				2,035,959
Land and Improvements				1,332,451
Buildings and Improvements				2,922,442
Costs Capitalized Subsequent to Acquisition(2)				1,762,611
Land and Improvements				1,368,294
Buildings and Improvements				4,649,210
Total	6,017,504			6,017,504
Accumulated Depreciation and Amortization	1,011,330			1,011,330
Real Estate:
Balance at end of the year	6,017,504
Accumulated Depreciation:
Balance at end of period	1,011,330
Summit II
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				1,699
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				0
Land and Improvements				1,699
Buildings and Improvements				0
Total	1,699			1,699
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	1,699
Accumulated Depreciation:
Balance at end of period	0
Potomac Yard Land Bay G - Parcel G
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				6,594
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				0
Land and Improvements				6,594
Buildings and Improvements				0
Total	6,594			6,594
Accumulated Depreciation and Amortization	0			0
Real Estate:
Balance at end of the year	6,594
Accumulated Depreciation:
Balance at end of period	0
Properties Held For Sale
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Encumbrances				0
Land and Improvements				8,293
Buildings and Improvements				0
Costs Capitalized Subsequent to Acquisition(2)				0
Land and Improvements				8,293
Buildings and Improvements				0
Total	8,293			8,293
Accumulated Depreciation and Amortization	0			$ 0
Real Estate:
Balance at end of the year	8,293
Accumulated Depreciation:
Balance at end of period	$ 0
Maximum
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Useful life	40 years