CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Total revenue	$ 3,318,414	$ 2,989,713	$ 2,514,617
Cost of revenue
Total cost of revenue	2,929,222	2,674,780	2,213,247
Gross profit	389,192	314,933	301,370
Selling, general and administrative expenses	272,776	220,400	217,374
Acquisition and integration expenses	60,045	0	0
Gain on sales of property and equipment	(7,672)	(4,182)	(8,358)
Operating income	64,043	98,715	92,354
Other (income) expense
Interest income	(6,082)	(4,742)	(3,225)
Interest expense	14,571	10,800	12,366
Equity in income of affiliates	(6,935)	(7,107)	(7,177)
Other income, net	(1,666)	(4,699)	(5,972)
Total other income	(112)	(5,748)	(4,008)
Income before provision for income taxes	64,155	104,463	96,362
Provision for income taxes	10,414	28,662	30,162
Net income	53,741	75,801	66,200
Amount attributable to non-controlling interests	(11,331)	(6,703)	(9,078)
Net income attributable to Granite Construction Incorporated	$ 42,410	$ 69,098	$ 57,122
Net income per share attributable to common shareholders (See Note 18)
Basic	$ 0.97	$ 1.74	$ 1.44
Diluted	$ 0.96	$ 1.71	$ 1.42
Weighted average shares of common stock
Basic	43,564	39,795	39,557
Diluted	44,025	40,372	40,225
Transportation [Member]
Revenue
Total revenue	$ 1,976,743	$ 1,947,420	$ 1,626,786
Cost of revenue
Total cost of revenue	1,786,698	1,777,285	1,464,957
Water [Member]
Revenue
Total revenue	338,250	133,699	161,282
Cost of revenue
Total cost of revenue	278,676	121,429	141,397
Specialty [Member]
Revenue
Total revenue	626,619	615,818	465,323
Cost of revenue
Total cost of revenue	535,731	528,372	382,865
Materials [Member]
Revenue
Total revenue	376,802	292,776	261,226
Cost of revenue
Total cost of revenue	$ 328,117	$ 247,694	$ 224,028