Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share, Basic, Two Class Method [Abstract]
Net income attributable to Granite, Earnings Per Share, Basic	$ 37,121	$ 36,468	$ 27,297	$ 32,407
Participating Securities, Distributed and Undistributed Earnings	181	469	184	491
Net Income (Loss) Available to Common Stockholders, Basic	36,940	35,999	27,113	31,916
Weighted Average Number of Shares Outstanding, Basic	38,518	38,172	38,418	38,092
Net income (loss) per share, basic	$ 0.96	$ 0.94	$ 0.71	$ 0.84
Earnings Per Share, Diluted, Two Class Method [Abstract]
Net income attributable to Granite, Earnings per Share, Diluted	37,121	36,468	27,297	32,407
Undistributed Earnings Allocated to Participating Securities	178	462	181	487
Net Income (Loss) Available to Common Stockholders, Diluted	$ 36,943	$ 36,006	$ 27,116	$ 31,920
Weighted average common shares outstanding, diluted	39,141	38,598	39,013	38,428
Net income (loss) per share, diluted	$ 0.94	$ 0.93	$ 0.70	$ 0.83