Additional Purchase Option Period

No definition available.

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- Definition

The number of common shares granted to underwriters pursuant to a 30-day option to purchase additional shares of common stock to cover over-allotments.

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of common shares sold pursuant to the underwriters' exercise of their option to purchase additional shares.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Percentage of Voting Interest

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The proceeds from issuance of common shares net of underwriting fees and offering costs.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount paid in cash and in shares pursuant to business acquisition.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

+ Details

Name:	us-gaap_CommonStockSharesIssued
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

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

- Definition

Per share or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

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

- Definition

Number of shares of stock issued during the period pursuant to acquisitions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Period Type:	duration

- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=grbk_ReverseRecapitalizationMember
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- Details

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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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- Details

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Organization and Basis of Presentation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Jul. 01, 2015	Oct. 27, 2014	Jul. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 23, 2015	Jun. 10, 2014
Class of Stock [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent				50.00%
Common Stock, Shares, Issued	17,000,000			50,598,901	48,955,909
Share Price	$ 10.00
AdditionalPurchaseOptionPeriod			30-day
CommonSharesGrantedToUnderwritersToCoverOverAllotments	841,500
CommonSharesSoldPursuantToUnderwritersOption							444,897
ProceedsFromIssuanceOfCommonSharesNetOfUnderwritingFeesAndOfferingCosts			$ 170,000
Repayments of Secured Debt				$ 0	$ 0	$ 150,000
Percentage of Voting Interest				51.00%
Common Stock
Class of Stock [Line Items]
Noncash portion of business acquisition				1,477,000
Reverse Recapitalization
Class of Stock [Line Items]
Proceeds from rights offering		$ 70,000
Reverse Recapitalization \| Common Stock \| LLC and LP \| JBGL
Class of Stock [Line Items]
Agreed upon purchase price, cash and equity		275,000						$ 275,000
Cash payment to acquired business		$ 191,800
Noncash portion of business acquisition		11,108,500
Issue price of shares		$ 7.49
Reverse Recapitalization \| Term Loan Facility \| Secured Debt \| Greenlight Capital, Inc
Class of Stock [Line Items]
Debt instrument, face amount		$ 150,000
Repayments of Secured Debt	$ 154,900
Percentage of Voting Interest		47.70%