Earnings Per Share (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share, Basic, Two Class Method [Abstract]
Net income (loss) attributable to Granite, Earnings Per Share, Basic	$ 36,468	$ 38,681	$ 32,407	$ (8,964)
Participating Securities, Distributed and Undistributed Earnings	469	903	491	0
Net Income (Loss) Available to Common Stockholders, Basic	35,999	37,778	31,916	(8,964)
Weighted Average Number of Shares Outstanding, Basic	38,172	37,865	38,092	37,802
Net income (loss) per share, basic	$ 0.94	$ 1	$ 0.84	$ (0.24)
Earnings Per Share, Diluted, Two Class Method [Abstract]
Net income (loss) attributable to Grainte, Earnings per Share, Diluted	36,468	38,681	32,407	(8,964)
Less: net income allocated to participating securities	462	898	487	0
Net Income (Loss) Available to Common Stockholders, Diluted	$ 36,006	$ 37,783	$ 31,920	$ (8,964)
Weighted average common shares outstanding, diluted	38,598	38,071	38,428	37,802
Net income (loss) per share, diluted	$ 0.93	$ 0.99	$ 0.83	$ (0.24)