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v2.4.1.9

Income Taxes (Narrative) (Details) (USD $) | 12 Months Ended | 0 Months Ended
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Oct. 27, 2014
Operating Loss Carryforwards [Line Items] |  |  |  |
Uncertain income tax positions | $ 0 us-gaap_UnrecognizedTaxBenefits |  |  |
Basis in partnerships | 26,123,000 grbk_DeferredTaxAssetsBasisinPartnership | 0 grbk_DeferredTaxAssetsBasisinPartnership |  |
One-time income tax benefit | 25,244,000 grbk_EffectiveIncomeTaxRateReconciliationChangeinTaxStatusAmount | 0 grbk_EffectiveIncomeTaxRateReconciliationChangeinTaxStatusAmount | 0 grbk_EffectiveIncomeTaxRateReconciliationChangeinTaxStatusAmount |
Deferred tax assets | 89,239,000 us-gaap_DeferredTaxAssetsNet | 0 us-gaap_DeferredTaxAssetsNet |  |
Deferred tax asset related to net operating loss carryforwards | 62,575,000 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic | 0 us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic |  |
Valuation allowance for deferred tax assets | 1,161,000 us-gaap_DeferredTaxAssetsValuationAllowance | 0 us-gaap_DeferredTaxAssetsValuationAllowance | 0 us-gaap_DeferredTaxAssetsValuationAllowance |
Federal |  |  |  |
Operating Loss Carryforwards [Line Items] |  |  |  |
Net operating loss carryforward | 178,800,000 us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_DomesticCountryMember |  |  |
Operating loss carryforward, expiration date | Dec. 31, 2029 |  |  |
State |  |  |  |
Operating Loss Carryforwards [Line Items] |  |  |  |
Net operating loss carryforward | 21,600,000 us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember |  |  |
Valuation allowance related to state loss carryforwards | 21,600,000 us-gaap_OperatingLossCarryforwardsValuationAllowance / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember |  |  |
Reverse Recapitalization |  |  |  |
Operating Loss Carryforwards [Line Items] |  |  |  |
One-time income tax benefit |  |  |  | 26,564,000 grbk_EffectiveIncomeTaxRateReconciliationChangeinTaxStatusAmount / us-gaap_BusinessAcquisitionAxis = grbk_ReverseRecapitalizationMember
Deferred tax assets |  |  |  | 63,900,000 us-gaap_DeferredTaxAssetsNet / us-gaap_BusinessAcquisitionAxis = grbk_ReverseRecapitalizationMember
Reverse Recapitalization | Federal |  |  |  |
Operating Loss Carryforwards [Line Items] |  |  |  |
Net operating loss carryforward |  |  |  | 182,300,000 us-gaap_OperatingLossCarryforwards / us-gaap_BusinessAcquisitionAxis = grbk_ReverseRecapitalizationMember / us-gaap_IncomeTaxAuthorityAxis = us-gaap_DomesticCountryMember
Reverse Recapitalization | State |  |  |  |
Operating Loss Carryforwards [Line Items] |  |  |  |
Net operating loss carryforward |  |  |  | $ 21,600,000 us-gaap_OperatingLossCarryforwards / us-gaap_BusinessAcquisitionAxis = grbk_ReverseRecapitalizationMember / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember

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- Definition Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319 + Details
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32621-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32632-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 25 -Paragraph 20 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=29652012&loc=d3e28680-109314 + Details
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319 + Details
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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319 + Details
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