Quarterly report pursuant to Section 13 or 15(d)

Equity and Mezzanine Equity - Additional Information (Detail)

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Equity and Mezzanine Equity - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2022
Jun. 30, 2021
Dec. 31, 2021
Feb. 20, 2020
Feb. 19, 2020
Jan. 29, 2020
Jan. 11, 2019
Class of Stock [Line Items]              
Temporary equity, contract terms, trigger change in control 50.00%            
Common stock, shares outstanding (in shares) 38,548,992   37,473,587 60,290,000 86,290,000    
Units held by noncontrolling owners (in shares) 256,994 256,994          
Gladstone Commercial Limited Partnership              
Class of Stock [Line Items]              
Company ownership percentage of voting securities 99.30%   99.30%        
Number of units redeemed in acquisition (in shares) 246,039            
Series D Preferred Stock              
Class of Stock [Line Items]              
Temporary equity, contract terms, minimum vote needed to trigger change in control from tender offer 90.00%            
Preferred Stock | Series E Preferred Stock              
Class of Stock [Line Items]              
Redeemable preferred stock, dividend rate 6.625%            
Preferred Stock | Series F Preferred Stock              
Class of Stock [Line Items]              
Redeemable preferred stock, shares issued (in shares) 62,883            
Consideration received $ 1.4            
Maximum remaining capacity to sell common stock under open market sale agreement $ 624.3            
Redeemable preferred stock, shares authorized (in shares)       26,000,000      
Common Stock ATM Program | Common Stock              
Class of Stock [Line Items]              
Universal registration statement, amount authorized           $ 63.0  
Common Stock ATM Program | Baird, Goldman Sachs, Stifel, Fifth Third, and U.S. Bancorp Investments, Inc. | Common Stock              
Class of Stock [Line Items]              
Redeemable preferred stock, shares issued (in shares) 900,000            
Common Stock ATM Program | Baird, Goldman Sachs, Stifel, and Fifth Third | Common Stock              
Class of Stock [Line Items]              
Consideration received $ 20.3            
Maximum remaining capacity to sell common stock under open market sale agreement 47.0            
2019 Universal Shelf              
Class of Stock [Line Items]              
Universal registration statement, amount authorized             $ 500.0
2020 Universal Shelf              
Class of Stock [Line Items]              
Universal registration statement, amount authorized $ 671.8         800.0  
2020 Universal Shelf | Preferred Stock | Series F Preferred Stock              
Class of Stock [Line Items]              
Universal registration statement, amount authorized           $ 636.5