Gladstone Commercial Corporation Annual report pursuant to Section 13 and 15(d)

Real Estate and Intangible Assets - Weighted Average Amortization Period for Intangible Assets Acquired and Liabilities Assumed (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	15 years 18 days	13 years 7 months 6 days
In-place Leases
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	13 years 6 months 22 days	11 years 8 months 12 days
Leasing Costs
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	13 years 6 months 22 days	11 years 8 months 12 days
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	18 years 11 months 19 days	19 years 3 months 18 days
Above Market Leases
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	10 years 7 months 28 days	10 years 4 months 24 days
Below Market Leases (1)
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	10 years 3 months 11 days	12 years 4 months 24 days