Dispositions and Discontinued Operations - Schedule of Assets and Liabilities and Results of Operations Related to Discontinued Operations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet:
Assets related to discontinued operations			$ 104,836
Other income (expense):
Real estate impairment loss			(42,000)	$ (46,000)
(Loss) income from discontinued operations, net		$ (5,075)	(33,811)	5,578
1899 Pennsylvania Avenue [Member]
Revenues:
Rental revenue		13,967
Other income		276
Total revenues		14,243
Expenses:
Operating		5,853
Depreciation and amortization		690	8,243
Total expenses		6,543
Other income (expense):
Income (loss) before gain or loss on sale of real estate		7,700
(Loss) gain on sale of real estate	[1]	(12,766)
(Loss) income before income taxes		(5,066)
Income tax expense		(9)
(Loss) income from discontinued operations, net		$ (5,075)
1899 Pennsylvania Avenue [Member] | Discontinued Operations Held for Sale [Member]
Balance Sheet:
Real estate, net			94,251
Deferred rent receivable			4,206
Deferred charges, net			804
Intangible assets, net			5,575
Assets related to discontinued operations			104,836
1899 Pennsylvania Avenue and Liberty Place [Member]
Revenues:
Rental revenue			24,969
Other income			457
Total revenues			25,426
Expenses:
Operating			10,134
Depreciation and amortization			8,243
Total expenses			18,377
Other income (expense):
Real estate impairment loss			(42,000)
Income (loss) before gain or loss on sale of real estate			(34,951)
(Loss) gain on sale of real estate	[1]		1,140
(Loss) income before income taxes			(33,811)
(Loss) income from discontinued operations, net			$ (33,811)
1899 Pennsylvania Avenue, Liberty Place, 425 Eye Street and 2099 Pennsylvania Avenue [Member]
Revenues:
Rental revenue				50,157
Other income				1,133
Total revenues				51,290
Expenses:
Operating				19,381
Depreciation and amortization				17,357
Total expenses				36,738
Other income (expense):
Interest and other income, net				181
Real estate impairment loss				(46,000)
Income (loss) before gain or loss on sale of real estate				(31,267)
(Loss) gain on sale of real estate	[1]			36,845
(Loss) income before income taxes				5,578
(Loss) income from discontinued operations, net				$ 5,578

[1] Represents the loss on sale of 1899 Pennsylvania Avenue in 2020, gain on sale of Liberty Place in 2019, and gain on sale of 425 Eye Street and 2099 Pennsylvania Avenue in 2018.