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(Loss) Earnings Per Share of Common Stock - Additional Information (Detail) - shares | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Earnings Per Share [Abstract] |  |  |  |
Weighted average number of operating partnership units held by noncontrolling limited partners (in shares) | 913,552 | 1,449,258 | 945,236 | 1,449,258

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- 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

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