Real Estate and Intangibles - Fair Values of Assets Acquired and Liabilities Assumed (Detail) - Operating Properties Acquired [Member] - DEA Sterling, VA, FDA College Park, MD, Various GSA Portland, OR, JSC - Suffolk, and FBI New Orleans [Member] $ in Thousands	Mar. 31, 2021 USD ($)
Business Acquisition [Line Items]
Total real estate	$ 57,993
Total intangible assets	6,084
Total intangible liabilities	(1)
Purchase price	64,076
Real Estate Investment [Member]
Business Acquisition [Line Items]
Land	4,860
Building	49,807
Acquired tenant improvements	3,326
In-place leases [Member]
Business Acquisition [Line Items]
Total intangible assets	4,490
Acquired Leasing Commissions [Member]
Business Acquisition [Line Items]
Total intangible assets	1,293
Above Market Leases [Member]
Business Acquisition [Line Items]
Total intangible assets	301
Below Market Leases [Member]
Business Acquisition [Line Items]
Total intangible liabilities	$ (1)