Label	Element	Value
Treasury Stock, Common [Member]
Stock Repurchased During Period, Shares	us-gaap_StockRepurchasedDuringPeriodShares	1,177,562
Restricted Stock [Member] \| Officer [Member]
ShareBasedAwardEquityInstrumentsOtherThanOptionsVestedInPeriod,Percent	grbk_ShareBasedAwardEquityInstrumentsOtherThanOptionsVestedInPeriodPercent	100.00%

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.