Revenue - Summary of Revenue from Tenant Construction Projects Disaggregated by Tenant Agency (Detail) - ASU 2014-09 [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	$ 1,265	$ 1,814
Food And Drug Administration ("FDA") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income		77
Federal Bureau of Investigation ("FBI") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	534	1,119
Department of Veteran Affairs ("VA") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	661	450
Military Entrance Processing Command (“MEPCOM”) [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	21
Immigration and Customs Enforcement ("ICE") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	20
Social Security Administration ("SSA") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	19	1
U.S. Citizenship and Immigration Services ("USCIS") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income		14
Drug Enforcement Administration ("DEA") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income		127
The Judiciary of the U.S. Government ("JUD") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	1	4
Internal Revenue Service ("IRS") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	3	6
U.S. Forest Service ("USFS") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income		$ 16
Bureau of the Fiscal Service ("BFS") [Member]
Disaggregation Of Revenue [Line Items]
Tenant Construction Project Income	$ 6