Quarterly report pursuant to Section 13 or 15(d)

Equity and Mezzanine Equity - Additional Information (Detail)

v3.21.2
Equity and Mezzanine Equity - Additional Information (Detail) - USD ($)
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2021
Jun. 28, 2021
Jun. 23, 2021
Nov. 30, 2019
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Feb. 20, 2020
Feb. 19, 2020
Jan. 29, 2020
Jan. 11, 2019
Class of Stock [Line Items]                          
Aggregate redemption price         $ 2,141,000                
Series D preferred stock offering costs write off         $ 2,141,000 $ 0 $ 2,141,000 $ 0          
Common stock, shares outstanding (in shares) 36,638,029       36,638,029   36,638,029   35,331,970 60,290,000 86,290,000    
Units held by noncontrolling owners (in shares)             256,994   503,033        
Gladstone Commercial Limited Partnership                          
Class of Stock [Line Items]                          
Company ownership percentage of voting securities 99.30%       99.30%   99.30%   98.60%        
Number of units redeemed in acquisition (in shares)       246,039                  
Series D Preferred Stock                          
Class of Stock [Line Items]                          
Redeemable preferred stock, dividend rate percentage (as percent)   7.00%                      
Temporary equity, contract terms, minimum vote needed to trigger change in control from tender offer (as percent) 90.00%       90.00%   90.00%            
Shares redeemed (in shares) 3,509,555                        
Redemption price (in usd per share) $ 25.1458333       $ 25.1458333   $ 25.1458333            
Aggregate redemption price $ 88,300,000                        
Series D preferred stock offering costs write off $ 2,100,000                        
Series F Preferred Stock                          
Class of Stock [Line Items]                          
Redeemable preferred stock, shares authorized (in shares) 26,000,000       26,000,000   26,000,000   26,000,000        
Series G Preferred Stock                          
Class of Stock [Line Items]                          
Redeemable preferred stock, dividend rate percentage (as percent)     6.00%                    
Redeemable preferred stock, shares authorized (in shares)     4,000,000                    
Preferred Stock | Series E Preferred Stock                          
Class of Stock [Line Items]                          
Redeemable preferred stock, dividend rate percentage (as percent)             6.625%            
Preferred Stock | Series F Preferred Stock                          
Class of Stock [Line Items]                          
Redeemable preferred stock, shares issued (in shares)             46,049            
Consideration received             $ 1,000,000.0            
Maximum remaining capacity to sell common stock under open market sale agreement $ 632,500,000       $ 632,500,000   632,500,000            
Redeemable preferred stock, shares authorized (in shares)                   26,000,000      
Baird, Goldman Sachs, Stifel, Fifth Third, and U.S. Bancorp Investments, Inc. | Preferred Stock | Series E 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       100,000,000.0   100,000,000.0            
Maximum remaining capacity to sell common stock under open market sale agreement 92,800,000       92,800,000   $ 92,800,000            
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)             1,000,000.0            
Consideration received             $ 19,400,000            
Maximum aggregate sales price of shares to be issued under open market sale agreement 250,000,000.0       250,000,000.0   250,000,000.0            
Maximum remaining capacity to sell common stock under open market sale agreement 164,300,000       164,300,000   164,300,000            
2019 Universal Shelf                          
Class of Stock [Line Items]                          
Universal registration statement, amount authorized 357,600,000       357,600,000   357,600,000           $ 500,000,000.0
2020 Universal Shelf                          
Class of Stock [Line Items]                          
Universal registration statement, amount authorized $ 696,000,000.0       $ 696,000,000.0   $ 696,000,000.0         $ 800,000,000.0  
2020 Universal Shelf | Preferred Stock | Series F Preferred Stock                          
Class of Stock [Line Items]                          
Universal registration statement, amount authorized                       $ 636,500,000  
Over-Allotment Option | Redeemable Preferred Stock                          
Class of Stock [Line Items]                          
Redeemable preferred stock, shares issued (in shares)   4,000,000                      
Public offering price (in usd per share)   $ 25.00                      
Consideration received   $ 100,000,000.0                      
Gross proceeds of the offering   $ 96,600,000