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(Loss) Earnings Per Share of Common Stock - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Weighted average number of operating partnership units held by non-controlling interest (in shares)	235,613	809,022

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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