CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 59,097	$ 48,055	$ 43,354	$ 40,476
Other comprehensive income, net of tax:
Net unrealized gain (loss) on derivatives	2,289	46	1,555	(163)
Less: reclassification for net (gains) losses included in interest expense	(1,719)	25	(157)	141
Net change	570	71	1,398	(22)
Foreign currency translation adjustments, net	249	98	(189)	633
Other comprehensive income	819	169	1,209	611
Comprehensive income	59,916	48,224	44,563	41,087
Non-controlling interests in comprehensive income	(3,425)	(2,073)	(7,490)	(4,151)
Comprehensive income attributable to Granite Construction Incorporated	$ 56,491	$ 46,151	$ 37,073	$ 36,936