Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v2.4.1.9
Stockholders' Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended 0 Months Ended
Mar. 31, 2015
Dec. 31, 2014
May 15, 2015
Apr. 02, 2014
Subsidiary, Sale of Stock [Line Items]        
Common stock, shares issued 7,753,717us-gaap_CommonStockSharesIssued 7,753,717us-gaap_CommonStockSharesIssued    
Maximum [Member]        
Subsidiary, Sale of Stock [Line Items]        
Securities allowed for issuance       $ 300.0land_ValueOfSecuritiesAllowedForIssuance
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Common Stock [Member]        
Subsidiary, Sale of Stock [Line Items]        
Common stock shares issued 1,223,453us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		1,223,453us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		   
Gross proceeds from issuance of common stock 15.0us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember 		     
Follow-on Offering [Member] | Subsequent Event [Member]        
Subsidiary, Sale of Stock [Line Items]        
Gross proceeds from issuance of common stock     $ 14.3us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
/ us-gaap_SubsidiarySaleOfStockAxis
= land_TwoThousandFourteenFollowOnOfferingCostMember 		 
Common stock, shares issued     1,250,000us-gaap_CommonStockSharesIssued
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
/ us-gaap_SubsidiarySaleOfStockAxis
= land_TwoThousandFourteenFollowOnOfferingCostMember 		 
Price per share     $ 11.40us-gaap_SharePrice
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
/ us-gaap_SubsidiarySaleOfStockAxis
= land_TwoThousandFourteenFollowOnOfferingCostMember