Annual report pursuant to Section 13 and 15(d)

Equity - Additional Information (Detail)

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Equity - Additional Information (Detail)
 12 Months Ended 21 Months Ended 30 Months Ended
May 31, 2018
USD ($)
$ / shares
shares
Apr. 12, 2017
USD ($)
security
Dec. 31, 2019
USD ($)
offering
$ / shares
shares
Dec. 31, 2018
USD ($)
offering
$ / shares
shares
Dec. 31, 2018
USD ($)
offering
$ / shares
shares
Sep. 30, 2019
USD ($)
Jan. 10, 2018
shares
Jan. 09, 2018
shares
Dec. 31, 2017
shares
Aug. 07, 2015
USD ($)
Sale of Stock [Line Items]                    
Stock authorized and unissued (in shares)             6,500,000      
Common stock, shares authorized (in shares)     91,500,000 91,500,000 91,500,000   91,500,000 98,000,000    
Preferred stock, liquidation value | $     $ 118,900,000 $ 28,609,825 $ 28,609,825          
Common stock, par value (in dollars per share) | $ / shares     $ 0.001 $ 0.001 $ 0.001          
Common stock, shares issued (in shares)     20,936,658 17,891,340 17,891,340          
Common stock, shares outstanding (in shares)     20,936,658 17,891,340 17,891,340          
Proceeds from issuance of preferred and common equity | $     $ 118,357,000 $ 74,417,000            
Redemptions of Series B Preferred Stock | $     340,000              
Payments of stock issuance costs | $     $ 9,186,000 $ 4,186,000            
Number of overnight public offerings | offering     1 2 2          
2017 Registration Statement                    
Sale of Stock [Line Items]                    
Maximum number of securities that can be sold (in securities) | security   2                
Proceeds from issuance of preferred and common equity | $           $ 96,700,000        
Common Stock                    
Sale of Stock [Line Items]                    
Common stock, shares outstanding (in shares)     20,936,658 17,891,340 17,891,340       13,791,574  
Common Stock | 2017 Registration Statement                    
Sale of Stock [Line Items]                    
Common stock, shares issued (in shares)     7,870,469              
Securities allowed for issuance (amount up to) | $   $ 300,000,000                
Common stock, issued (in shares)         1,215,565          
Gladstone Land Limited Partnership                    
Sale of Stock [Line Items]                    
OP units held by non-controlling limited partners (in shares)     288,303 570,879            
OP units held by non-controlling interest limited partners (in shares)     0              
Series B Preferred Stock                    
Sale of Stock [Line Items]                    
Preferred stock, shares authorized (in shares)     6,500,000 6,500,000 6,500,000          
Preferred stock, par value (in dollars per share) | $ / shares     $ 0.001 $ 0.001 $ 0.001          
Preferred stock, shares issued (in shares)     4,755,869 1,144,393 1,144,393          
Preferred stock, shares outstanding (in shares)     4,755,869 1,144,393 1,144,393          
Series B Preferred Stock | 2017 Registration Statement                    
Sale of Stock [Line Items]                    
Proceeds from issuance of preferred and common equity | $           $ 117,300,000        
Series B Preferred Stock | Preferred Stock                    
Sale of Stock [Line Items]                    
Preferred stock, shares outstanding (in shares)     4,755,869 1,144,393 1,144,393       0  
Securities allowed for issuance (amount up to) | $ $ 150,000,000                  
Maximum amount authorized in Primary Offering (in shares) 6,000,000                  
Average sales price of common stock sold (in dollars per share) | $ / shares $ 25                  
Proceeds from issuance and preferred stock | $ $ 131,300,000                  
Redemption of preferred stock (in shares)     14,600              
Redemption price (in dollars per share) | $ / shares     $ 23.30              
Redemptions of Series B Preferred Stock | $     $ 340,000              
Payments of stock issuance costs | $     $ 1,200,000              
Series B Preferred Stock | Preferred Stock | 2017 Registration Statement                    
Sale of Stock [Line Items]                    
Common stock, shares issued (in shares)     4,770,469              
Common Stock | ATM Program                    
Sale of Stock [Line Items]                    
Common stock, value authorized | $                   $ 30,000,000.0
OP Unit Holder                    
Sale of Stock [Line Items]                    
Company's ownership percent (as percent)     98.60% 96.90% 96.90%          
Minimum period required to exercise, in months     12 months