Annual report pursuant to Section 13 and 15(d)

Real Estate and Intangible Assets - Significant Existing Real Estate Activity (Narrative) (Detail)

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Real Estate and Intangible Assets - Significant Existing Real Estate Activity (Narrative) (Detail)
 1 Months Ended 12 Months Ended 25 Months Ended 118 Months Ended 184 Months Ended
Sep. 30, 2015
a
well
Apr. 30, 2014
property
Dec. 31, 2017
USD ($)
a
farm
lease
Dec. 31, 2016
USD ($)
a
Dec. 31, 2015
USD ($)
Sep. 30, 2017
USD ($)
May 31, 2027
USD ($)
Jan. 09, 2031
USD ($)
Oct. 17, 2017
USD ($)
Real Estate Properties [Line Items]                  
Operating leases, income statement, lease revenue     $ 25,111,000 $ 17,306,000 $ 11,888,000        
Total Acres | a     63,014 50,592          
General and administrative expenses     $ 1,628,000 $ 1,378,000 $ 1,247,000        
Number of properties damaged in fire | property   2              
Property And Casualty Recovery                  
Real Estate Properties [Line Items]                  
Unusual or infrequent item, or both, insurance proceeds     $ 97,000            
Unsecured Debt | Gladstone Land Advisers, Inc.                  
Real Estate Properties [Line Items]                  
Debt instrument, face amount                 $ 1,700,000
Interest rate (as percent)                 5.00%
California and Florida                  
Real Estate Properties [Line Items]                  
Lessee, number of leases extended or renewed | lease     10            
Lessee, number of farms with extended or renewed | farm     9            
Payments for tenant improvements     $ 2,017            
Operating leases, income statement, lease revenue     2,018            
Annualized straight line rental income     2,200,000            
Increase (decrease) in rental income     $ (167,000)            
Percentage increase (decrease) in rental revenue     (7.00%)            
Santa Cruz County, California                  
Real Estate Properties [Line Items]                  
Annualized straight line rental income     $ 605,000            
Percentage increase (decrease) in rental revenue     10.90%            
General and administrative expenses     $ 99,000            
California                  
Real Estate Properties [Line Items]                  
Operating leases, income statement, lease revenue     $ 12,000,000 $ 9,829,000          
Total Acres | a 854   8,080 6,713          
Real estate property area of development removal of old grape vine yards | a 274                
Number of new drilling wells | well 4                
Area of new almond trees | a 800                
Payments for capital improvements     $ 660,000     $ 8,400,000      
California | Forecast                  
Real Estate Properties [Line Items]                  
Operating leases, income statement, lease revenue             $ 2,300,000 $ 5,200,000  
Ventura County, California                  
Real Estate Properties [Line Items]                  
Total Acres | a 169