Investments in Affiliates Equity Method Investment Summarized Income Statement Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Granite’s interest in affiliates’ net income	$ (901)	$ (1,304)	$ (1,988)
Other Affiliates [Member] | Joint Venture Unconsolidated [Member]
Revenue	46,597	42,563	52,342
Gross profit	10,315	3,487	13,254
Income (loss) before taxes	3,647	(686)	1,318
Net income (loss)	3,647	(686)	1,318
Granite’s interest in affiliates’ net income	$ 901	$ 1,304	$ 1,988