Gladstone Commercial Corporation Quarterly report pursuant to Section 13 or 15(d)

Real Estate and Intangible Assets - Carrying Value of Intangible Assets and Accumulated Amortization (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Below market leases and deferred revenue, gross	$ (39,421)	$ (38,319)
Below market leases and deferred revenue, accumulated amortization	19,295	17,686
Lease Intangibles
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	244,631	241,229
Accumulated Amortization	(130,574)	(123,850)
In-place leases
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	100,470	99,254
Accumulated Amortization	(56,983)	(54,168)
Leasing costs
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	75,310	73,707
Accumulated Amortization	(39,751)	(37,801)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	68,851	68,268
Accumulated Amortization	(33,840)	(31,881)
Above market leases
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	15,203	15,076
Accumulated Amortization	$ (10,883)	$ (10,670)