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Business and Organization - Additional Information (Detail)	Sep. 30, 2020	Dec. 31, 2019
OP Unit Holder
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Company's ownership percent (as percent)	100.00%	98.60%

X

- Definition

Organization consolidation and presentation of financial statements disclosure.

+ References

No definition available.

+ Details

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Namespace Prefix:	land_
Data Type:	xbrli:stringItemType
Balance Type:	na
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X

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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- Details

Name:	srt_OwnershipAxis=land_OPUnitHolderMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: