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	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Below market leases and deferred revenue, gross	$ (39,481)	$ (38,319)
Below market leases and deferred revenue, accumulated amortization	20,110	17,686
Lease Intangibles
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	246,393	241,229
Accumulated Amortization	(135,309)	(123,850)
In-place leases
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	100,779	99,254
Accumulated Amortization	(58,955)	(54,168)
Leasing costs
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	76,602	73,707
Accumulated Amortization	(41,224)	(37,801)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	69,012	68,268
Accumulated Amortization	(35,130)	(31,881)
Above market leases
Finite-Lived Intangible Assets [Line Items]
Lease Intangibles	15,460	15,076
Accumulated Amortization	$ (11,097)	$ (10,670)