Discontinued Operations - Schedule of Assets and Liabilities and Results of Operations Related to Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Balance Sheets:
Assets related to discontinued operations	$ 103,915		$ 103,915		$ 104,836
Expenses:
Income from discontinued operations, net	2,147	$ 2,056	3,668	$ 4,162
1899 Pennsylvania Avenue [Member]
Revenues:
Rental revenue	3,515		7,078
Fee and other income	31		130
Total revenues	3,546		7,208
Expenses:
Operating	1,399		2,850
Depreciation and amortization			690
Total expenses	1,399		3,540
Income from discontinued operations, net	2,147		3,668
1899 Pennsylvania Avenue [Member] | Discontinued Operations Held for Sale [Member]
Balance Sheets:
Real estate, net	93,837		93,837		94,251
Deferred rent receivable	4,008		4,008		4,206
Deferred charges, net	780		780		804
Intangible assets, net	5,290		5,290		5,575
Assets related to discontinued operations	$ 103,915		$ 103,915		$ 104,836
1899 Pennsylvania Avenue and Liberty Place [Member]
Revenues:
Rental revenue		7,096		14,371
Fee and other income		144		272
Total revenues		7,240		14,643
Expenses:
Operating		2,836		5,756
Depreciation and amortization		2,348		4,725
Total expenses		5,184		10,481
Income from discontinued operations, net		$ 2,056		$ 4,162