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

Quarterly report pursuant to Section 13 or 15(d)

Mortgage Notes Payable and Credit Facility - Additional Information (Detail)

Mortgage Notes Payable and Credit Facility - Additional Information (Detail)		1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 27, 2017 USD ($)	Oct. 31, 2015 USD ($)	Sep. 30, 2018 USD ($) mortgage property	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) mortgage property	Sep. 30, 2018 USD ($) mortgage property	Sep. 30, 2018 USD ($) mortgage property	Sep. 30, 2018 USD ($) mortgage property	Sep. 30, 2017 USD ($)	Sep. 18, 2018 USD ($)	Jul. 23, 2018 USD ($)	Apr. 18, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 05, 2015 USD ($)	Aug. 31, 2013 USD ($)
Debt Instrument [Line Items]
Number of properties collateralized in mortgage notes payable \| property			99		99	99	99	99
Number of long-term mortgages repaid					1		1
Number of properties repaid to collateralized mortgages notes payable \| mortgage					1
Number of properties collateralized \| property							2
Payments of deferred financing costs						$ 345,000			$ 992,000
Fair value of mortgage notes payable			$ 435,900,000		$ 435,900,000	435,900,000	$ 435,900,000	$ 435,900,000
Maximum borrowing capacity	$ 75,000,000.0														$ 25,000,000.0
Extension fee on initial maturity (as percent)	0.25%
Debt instrument fees incurred	$ 900,000
Line of credit outstanding			$ 30,334,000		$ 30,334,000	$ 30,334,000	$ 30,334,000	$ 30,334,000					$ 20,715,000
Weighted average interest rate on debt outstanding (as percent)			4.66%		4.66%	4.66%	4.66%	4.66%
Term Loan Facility
Debt Instrument [Line Items]
Term of debt	5 years
Extension fee on initial maturity (as percent)		0.05%
Revolving credit facility
Debt Instrument [Line Items]
Term of debt	4 years
Line of credit
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 85,000,000.0												$ 85,000,000.0
Line of credit outstanding			$ 105,900,000		$ 105,900,000	$ 105,900,000	$ 105,900,000	$ 105,900,000
Weighted average interest rate (as percent)			3.97%		3.97%	3.97%	3.97%	3.97%
Letters of credit, outstanding			$ 1,200,000		$ 1,200,000	$ 1,200,000	$ 1,200,000	$ 1,200,000
Maximum additional amount that can be drawn under Line of Credit			$ 49,300,000		$ 49,300,000	$ 49,300,000	$ 49,300,000	$ 49,300,000
Line of credit \| Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 25,000,000.0
Term of debt		5 years
Letter of credit
Debt Instrument [Line Items]
Weighted average interest rate on debt outstanding (as percent)			1.75%		1.75%	1.75%	1.75%	1.75%
Variable rate mortgage loans
Debt Instrument [Line Items]
Number of properties collateralized in mortgage notes payable \| property			18		18	18	18	18
Carrying value			$ 61,115,000		$ 61,115,000	$ 61,115,000	$ 61,115,000	$ 61,115,000		$ 3,600,000.0	$ 4,000,000.0	$ 13,000,000.0	69,302,000
Mortgage notes payable
Debt Instrument [Line Items]
Number of mortgage notes payable \| mortgage			46		46	46	46	46
Number of properties collateralized in mortgage notes payable \| property			67		67	67	67	67
Net book value of collateralized mortgage properties			$ 638,900,000		$ 638,900,000	$ 638,900,000	$ 638,900,000	$ 638,900,000
Recourse amount of mortgage notes payable			10,200,000		10,200,000	10,200,000	10,200,000	$ 10,200,000
Percentage of debt recourse (as percent)								2.30%
Carrying value			$ 441,735,000		$ 441,735,000	$ 441,735,000	$ 441,735,000	$ 441,735,000
Weighted average interest rate on debt outstanding (as percent)			4.52%		4.52%	4.52%	4.52%	4.52%
Issued and assumed mortgage notes payable
Debt Instrument [Line Items]
Number of mortgage notes payable \| mortgage			2		2	2	2	2
Number of properties collateralized in mortgage notes payable \| property			2		2	2	2	2
Fixed rate mortgage loans
Debt Instrument [Line Items]
Number of properties collateralized in mortgage notes payable \| property			49		49	49	49	49
Stated interest rate (as percent)			5.75%		5.75%	5.75%	5.75%	5.75%
Carrying value			$ 380,620,000		$ 380,620,000	$ 380,620,000	$ 380,620,000	$ 380,620,000					$ 383,189,000
Payments of deferred financing costs			$ 100,000	$ 600,000		$ 300,000			$ 1,000,000
LIBOR
Debt Instrument [Line Items]
Spread on LIBOR (as percent)	2.75%
LIBOR \| Variable rate mortgage loans
Debt Instrument [Line Items]
Spread on LIBOR (as percent)								2.25%