Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share, Basic, Two Class Method [Abstract]
Net income (loss) attributable to Granite, Earnings Per Share, Basic	$ 1,949	$ 4,946	$ (9,824)	$ (4,061)
Participating Securities, Distributed and Undistributed Earnings	10	65	0	0
Net Income (Loss) Available to Common Stockholders, Basic	1,939	4,881	(9,824)	(4,061)
Weighted Average Number of Shares Outstanding, Basic	38,471	38,140	38,368	38,052
Net income (loss) per share, basic	$ 0.05	$ 0.13	$ (0.26)	$ (0.11)
Earnings Per Share, Diluted, Two Class Method [Abstract]
Net income (loss) attributable to Granite, Earnings per Share, Diluted	1,949	4,946	(9,824)	(4,061)
Undistributed Earnings Allocated to Participating Securities	10	65	0	0
Net Income (Loss) Available to Common Stockholders, Diluted	$ 1,939	$ 4,881	$ (9,824)	$ (4,061)
Weighted average common shares outstanding, diluted	39,151	38,479	38,368	38,052
Net income (loss) per share, diluted	$ 0.05	$ 0.13	$ (0.26)	$ (0.11)