Earnest Money Deposits (Schedule of Expected Land Purchase Payments Under Option Agreements) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Other Restricted Assets [Abstract]
2017	$ 39,508
2018	33,444
2019	11,073
Total	$ 84,025	$ 79,300

Land under Purchase Options, Expected Purchase Payments, Next Twelve Months

No definition available.

Name:	grbk_LandunderPurchaseOptionsExpectedPurchasePaymentsNextTwelveMonths
Namespace Prefix:	grbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant