SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Reconciliation of Carrying Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Initial Cost to Company
Land	$ 44,060
Buildings and Improvements	272,927
Costs Capitalized Subsequent to Acquisition, Net	94,827
Impairment/Write Downs	(10,104)
Cost Amount Carried at Close of Period
Land	44,060
Buildings and Improvements	357,650
Total	401,710
Accumulated Depreciation	143,319	$ 202,700	$ 375,968	$ 450,718
1225 Seventeenth Street
Initial Cost to Company
Land	22,400
Buildings and Improvements	110,090
Costs Capitalized Subsequent to Acquisition, Net	41,742
Impairment/Write Downs	(3,018)
Cost Amount Carried at Close of Period
Land	22,400
Buildings and Improvements	148,814
Total	171,214
Accumulated Depreciation	46,258
1250 H Street, NW
Initial Cost to Company
Land	5,975
Buildings and Improvements	53,778
Costs Capitalized Subsequent to Acquisition, Net	18,917
Impairment/Write Downs	(2,778)
Cost Amount Carried at Close of Period
Land	5,975
Buildings and Improvements	69,917
Total	75,892
Accumulated Depreciation	36,538
206 East 9th Street
Initial Cost to Company
Land	7,900
Buildings and Improvements	38,533
Costs Capitalized Subsequent to Acquisition, Net	6,872
Impairment/Write Downs	(837)
Cost Amount Carried at Close of Period
Land	7,900
Buildings and Improvements	44,568
Total	52,468
Accumulated Depreciation	10,108
Bridgepoint Square
Initial Cost to Company
Land	7,785
Buildings and Improvements	70,526
Costs Capitalized Subsequent to Acquisition, Net	27,296
Impairment/Write Downs	(3,471)
Cost Amount Carried at Close of Period
Land	7,785
Buildings and Improvements	94,351
Total	102,136
Accumulated Depreciation	$ 50,415