Earnest Money Deposits (Schedule of Expected Land Purchase Payments Under Option Agreements) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other Restricted Assets [Abstract]
2016	$ 40,667
2017	24,031
2018	13,047
2019	1,593
Total	$ 79,338	$ 71,600

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