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Earnings Per Share of Common Stock - Additional Information (Detail) - shares | 3 Months Ended |
--- | --- | ---
Mar. 31, 2016 | Dec. 31, 2015
Earnings Per Share [Abstract] |  |
Weighted average number of operating partnership units held by noncontrolling limited partners | 237,698 |
Operating partnership units held |  | 0

X
- Definition Operating Partnership Units Outstanding + References No definition available. + Details
Name: | land_OperatingPartnershipUnitsOutstanding
Namespace Prefix: | land_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Weighted Average Number of Operating Partnership Units Held By Noncontrolling Interest + References No definition available. + Details
Name: | land_WeightedAverageNumberOfOperatingPartnershipUnitsHeldByNoncontrollingInterest
Namespace Prefix: | land_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_EarningsPerShareAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration