Acquisitions - Pro-forma Financial Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Business Combinations [Abstract]
Revenue	$ 2,388,790	$ 2,289,043
Net income including non-controlling interests	82,914	78,344
Net income attributable to Granite	$ 58,225	$ 55,993
Basic net income per share (in dollars per share)	$ 1.50	$ 1.46
Diluted net income per share (in dollars per share)	$ 1.48	$ 1.45