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

Annual report pursuant to Section 13 and 15(d)

Equity and Mezzanine Equity - Additional Information (Detail)

Equity and Mezzanine Equity - Additional Information (Detail) $ in Thousands					1 Months Ended		12 Months Ended
	Jan. 08, 2020 USD ($) ft² shares	Nov. 14, 2019 USD ($) ft²	Feb. 28, 2019 USD ($) ft²	Oct. 30, 2018 USD ($) ft² property shares	Feb. 29, 2020	Nov. 30, 2019 shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Feb. 20, 2020 shares	Feb. 19, 2020 shares	Jan. 29, 2020 USD ($)	Dec. 03, 2019 USD ($)	Jan. 11, 2019 USD ($)
Class of Stock [Line Items]
Common stock, shares outstanding (in shares) \| shares							35,331,970	32,593,651	60,290,000	86,290,000
Aggregate Purchase Price							$ 129,974	$ 130,313
Units held by noncontrolling owners (in shares) \| shares							503,033	479,637
Series D Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Minimum vote need to trigger change in control from tender offer (as percent)							90.00%
Preferred Stock \| Series D Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate (as percent)							7.00%
Preferred Stock \| Series E Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate (as percent)							6.625%
Preferred Stock \| Series F Preferred Stock
Class of Stock [Line Items]
Number of shares sold (in shares) \| shares							100,000
Net proceeds from sale of shares							$ 2,700
Open market dale agreement, value of remaining capacity							633,600
Preferred stock, dividend rate (as percent)					6.00%
Redeemable preferred stock, shares authorized (in shares) \| shares									26,000,000
2019 Universal Shelf
Class of Stock [Line Items]
Universal registration statement, amount authorized							377,200						$ 500,000
2020 Universal Shelf
Class of Stock [Line Items]
Universal registration statement, amount authorized							$ 797,100				$ 800,000
2020 Universal Shelf \| Preferred Stock \| Series F Preferred Stock
Class of Stock [Line Items]
Universal registration statement, amount authorized											$ 636,500
Baird, Goldman Sachs, Stifel, and Fifth Third \| Common Stock ATM Program \| Common Stock and Non-controlling OP Units
Class of Stock [Line Items]
Maximum aggregate sales price of shares to be issued under open market sale agreement												$ 250,000
Number of shares sold (in shares) \| shares							2,700,000
Net proceeds from sale of shares							$ 52,800
Open market dale agreement, value of remaining capacity							183,900
Baird, Goldman Sachs, Stifel, Fifth Third, and U.S. Bancorp Investments, Inc. \| Series E Preferred Stock ATM Program
Class of Stock [Line Items]
Maximum aggregate sales price of shares to be issued under open market sale agreement							$ 100,000
Number of shares sold (in shares) \| shares							300,000
Net proceeds from sale of shares							$ 7,100
Open market dale agreement, value of remaining capacity							$ 92,800
Operating Partnership
Class of Stock [Line Items]
Company ownership percentage of voting securities							98.60%	98.60%
Number of units issued in acquisition (in shares) \| shares	23,396			742,937
Number of units redeemed in acquisition (in shares) \| shares						263,300
Detroit, Michigan
Class of Stock [Line Items]
Aggregate Square Footage \| ft²				218,703
Number of properties in portfolio \| property				2
Aggregate Purchase Price				$ 21,700
Indianapolis, Indiana
Class of Stock [Line Items]
Aggregate Square Footage \| ft²	64,800	231,509	34,800
Aggregate Purchase Price	$ 5,300	$ 8,200	$ 3,600