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Carrying value of inventory evaluated for impairment

No definition available.

Name:	grbk_CarryingValueOfInventoryEvaluatedForImpairment
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Deposits and pre-acquisition costs written off related to option contracts we abandoned.

No definition available.

Name:	grbk_EarnestMoneyDepositsandPreacquisitionCostsWrittenOff
Namespace Prefix:	grbk_
Data Type:	xbrli:monetaryItemType
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Finished Homes and Homes under Construction

No definition available.

Name:	grbk_FinishedHomesandHomesunderConstruction
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Land held for future development

No definition available.

Name:	grbk_LandHeldForFutureDevelopment
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- References

No definition available.

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Carrying amount as of the balance sheet date of parcels of land held for sale, and on which the entity has no intention or no further intention to perform construction activities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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Total of (1) improvements, (2) held-for-sale, (3) land and land under development, (4) construction-in-process, (5) mortgage loans held-in-inventory, and (6) other real estate investments which are considered inventory due to being held for sale or disposition.

No definition available.

Name:	us-gaap_InventoryRealEstate
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Carrying amount as of the balance sheet date, net of valuation allowances and impairment losses, of costs of land expected to be developed in the near term plus capitalized costs of development, for purposes of selling completed units to home buyers or commercial or industrial entities.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1