Annual report pursuant to Section 13 and 15(d)

Borrowings - Summary of Mortgage Note Payable and Line of Credit (Detail)

v2.4.1.9
Borrowings - Summary of Mortgage Note Payable and Line of Credit (Detail) (USD $)
 12 Months Ended
Dec. 31, 2014
May 09, 2014
Dec. 31, 2013
Debt Instrument [Line Items]      
Principal Outstanding $ 86,417,361us-gaap_LongTermDebt   $ 43,154,165us-gaap_LongTermDebt
Undrawn Commitment 125,993,002us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount   4,685,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
New Line of Credit [Member]      
Debt Instrument [Line Items]      
Maturity Date Apr. 05, 2024    
MetLife [Member]      
Debt Instrument [Line Items]      
Initial Commitment   125,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember 		 
Maturity Date May 09, 2014    
MetLife [Member] | Mortgage Note Payable [Member]      
Debt Instrument [Line Items]      
Issuer MetLife    
Date of Issuance Dec. 30, 2010    
Initial Commitment 45,200,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_NotesPayableToBanksMember 		100,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_NotesPayableToBanksMember 		 
Maturity Date Jan. 05, 2026    
Principal Outstanding     43,054,165us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_NotesPayableToBanksMember
Stated Interest Rate 3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_NotesPayableToBanksMember 		  3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_NotesPayableToBanksMember
MetLife [Member] | New Line of Credit [Member]      
Debt Instrument [Line Items]      
Issuer MetLife    
Date of Issuance May 23, 2012    
Initial Commitment 4,785,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember 		25,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember 		 
Maturity Date Apr. 05, 2017    
Principal Outstanding     100,000us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
Stated Interest Rate     3.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
Undrawn Commitment     4,685,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
MetLife [Member] | Mortgage Note Payable [Member]      
Debt Instrument [Line Items]      
Issuer MetLife    
Date of Issuance May 09, 2014    
Initial Commitment 100,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewNotesPayableMember 		   
Maturity Date Jan. 05, 2029    
Principal Outstanding 66,331,998us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewNotesPayableMember 		   
Stated Interest Rate 3.61%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewNotesPayableMember 		   
Undrawn Commitment 33,668,002us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewNotesPayableMember 		   
MetLife [Member] | New Line of Credit [Member]      
Debt Instrument [Line Items]      
Issuer MetLife    
Date of Issuance May 09, 2014    
Initial Commitment 25,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewLineOfCreditMember 		   
Maturity Date Apr. 05, 2024    
Principal Outstanding 4,000,000us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewLineOfCreditMember 		   
Stated Interest Rate 2.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewLineOfCreditMember 		   
Undrawn Commitment 21,000,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_MetlifeMember
/ us-gaap_LongtermDebtTypeAxis
= land_NewLineOfCreditMember 		   
Farm Credit [Member]      
Debt Instrument [Line Items]      
Maturity Date Aug. 01, 2034    
Stated Interest Rate 3.53%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember 		   
Farm Credit [Member] | Mortgage Note Payable [Member]      
Debt Instrument [Line Items]      
Issuer Farm Credit    
Date of Issuance Sep. 19, 2014    
Initial Commitment 2,655,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableOneMember 		   
Maturity Date Aug. 01, 2034    
Principal Outstanding 2,655,000us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableOneMember 		   
Stated Interest Rate 3.52%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableOneMember 		   
Farm Credit [Member] | Mortgage Note Payable [Member]      
Debt Instrument [Line Items]      
Issuer Farm Credit    
Date of Issuance Sep. 19, 2014    
Initial Commitment 1,599,600us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableTwoMember 		   
Maturity Date Aug. 01, 2034    
Principal Outstanding 1,599,600us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableTwoMember 		   
Stated Interest Rate 3.52%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableTwoMember 		   
Farm Credit [Member] | Mortgage Note Payable [Member]      
Debt Instrument [Line Items]      
Issuer Farm Credit    
Date of Issuance Sep. 29, 2014    
Initial Commitment 8,259,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableThreeMember 		   
Maturity Date Aug. 01, 2034    
Principal Outstanding 8,155,763us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableThreeMember 		   
Stated Interest Rate 3.54%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmCreditMember
/ us-gaap_LongtermDebtTypeAxis
= land_MortgageNotesPayableThreeMember 		   
Farmer Mac [Member] | Bonds Payable [Member]      
Debt Instrument [Line Items]      
Issuer Farmer Mac    
Date of Issuance Dec. 11, 2014    
Initial Commitment 75,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmerMacMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_CorporateBondSecuritiesMember 		   
Maturity Date Dec. 11, 2019    
Principal Outstanding 3,675,000us-gaap_LongTermDebt
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmerMacMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_CorporateBondSecuritiesMember 		   
Stated Interest Rate 3.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmerMacMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_CorporateBondSecuritiesMember 		   
Undrawn Commitment $ 71,325,000us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
/ us-gaap_LineOfCreditFacilityAxis
= land_FarmerMacMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_CorporateBondSecuritiesMember