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)					12 Months Ended
	Oct. 28, 2019 USD ($) $ / shares shares	Oct. 04, 2019 USD ($) $ / shares shares	Oct. 30, 2018 USD ($) ft² property shares	Apr. 11, 2018 shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 03, 2019 USD ($)	Dec. 02, 2019 shares	Sep. 30, 2019 USD ($)	Sep. 27, 2019 shares	Sep. 26, 2019 shares	Jan. 11, 2019 USD ($)	Dec. 31, 2016 USD ($)	Feb. 29, 2016 USD ($)
Class of Stock [Line Items]
Authorized but unissued shares reclassified from senior common stock to common stock				3,500,000
Senior common stock, authorized shares unissued (in shares)				57,969
Capital stock, shares authorized				100,000,000
Common stock, shares authorized (in shares)				87,700,000	86,290,000	87,700,000		86,290,000		83,700,000	87,700,000
Common stock, shares authorized but unissued (in shares)								2,590,000
Aggregate Purchase Price \| $					$ 130,313,000	$ 63,245,000
Units held by noncontrolling owners (in shares)					479,637	742,937
Series A Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized but unissued (in shares)								2,600,000
Series B Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized but unissued (in shares)								2,750,000
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%
Redeemable preferred stock, shares authorized (in shares)								6,000,000
Senior Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)								950,000
Series E Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Redeemable preferred stock, shares issued (in shares)		2,760,000
Public offering price (in dollars per share) \| $ / shares		$ 25.00
Gross proceeds of the offering \| $		$ 69,000,000
Net proceeds, after deducting offering expenses \| $		$ 66,600,000
Preferred stock, shares authorized but unissued (in shares)								10,000
Redeemable preferred stock, shares authorized (in shares)								6,760,000		4,000,000
Series A and B Preferred Stock
Class of Stock [Line Items]
Redeemable preferred stock, shares issued (in shares)					0	2,264,000
Redeemable preferred stock, shares authorized (in shares)					0	5,350,000
Preferred Stock \| Series A Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Treasury stock, shares, acquired	1,000,000
Preferred stock, redemption price per share (in usd per share) \| $ / shares	$ 25.1506944
Preferred Stock \| Series B Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Treasury stock, shares, acquired	1,264,000
Preferred stock, redemption price per share (in usd per share) \| $ / shares	$ 25.1458333
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 A and B Preferred Stock
Class of Stock [Line Items]
Net proceeds from sale of shares \| $	$ 2,700,000
Preferred stock, redemption price \| $	$ 56,900,000
2019 Universal Shelf
Class of Stock [Line Items]
Universal registration statement, amount authorized \| $									$ 438,000,000			$ 500,000,000
Cantor Fitzgerald & Co \| Preferred Stock \| Series B Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Maximum aggregate sales price of shares to be issued under open market sale agreement \| $									$ 40,000,000.0
Preferred stock, dividend rate (as percent)					7.50%
Cantor Fitzgerald & Co \| Preferred Stock \| Series D Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Maximum aggregate sales price of shares to be issued under open market sale agreement \| $													$ 50,000,000.0
Cantor Fitzgerald & Co \| Preferred Stock \| Series E Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Maximum aggregate sales price of shares to be issued under open market sale agreement \| $							$ 100,000,000.0
Cantor Fitzgerald & Co \| 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 \| $														$ 250,000,000
Number of shares sold (in shares)					3,000,000
Net proceeds from sale of shares \| $					$ 64,500,000
Open market dale agreement, value of remaining capacity \| $					$ 237,500,000
Cantor Fitzgerald & Co \| Series A and B Preferred Stock ATM Programs \| Preferred Stock \| Series A Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate (as percent)					7.75%
Operating Partnership
Class of Stock [Line Items]
Company ownership percentage of voting securities					98.60%	97.50%
Number of units issued in acquisition (in shares)			742,937
Number of units redeemed in acquisition (in shares)			263,300
Detroit, Michigan
Class of Stock [Line Items]
Number of units issued in acquisition (in shares)			742,937
Aggregate Square Footage \| ft²			218,703
Aggregate Purchase Price \| $			$ 21,700,000
Number of properties in portfolio \| property			2