Contributions of LLC Members

No definition available.

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Namespace Prefix:	grbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Letters of Credit Issued

+ References

No definition available.

+ Details

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Namespace Prefix:	grbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Details

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Subsequent Events (Details) - USD ($) $ in Millions	Oct. 17, 2019	Oct. 11, 2019	Sep. 30, 2019	Jul. 23, 2019
Subsequent Event [Line Items]
Letters of Credit Issued				$ 1.3
Line of Credit Facility, Remaining Borrowing Capacity			$ 71.8
Subsequent Event [Member]
Subsequent Event [Line Items]
Letters of Credit Issued		$ 5.7
Line of Credit Facility, Remaining Borrowing Capacity		$ 66.1
Contributions of LLC Members	$ 5.0
Equity Method Investment, Ownership Percentage	50.00%