CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue
Total revenue	$ 807,119	$ 762,913	$ 1,370,498	$ 1,231,313
Cost of revenue
Total cost of revenue	726,750	688,343	1,233,846	1,131,617
Gross profit	80,369	74,570	136,652	99,696
Selling, general and administrative expenses	61,316	51,388	122,568	113,225
Acquisition and integration expenses	26,287	0	34,696	0
Gain on sales of property and equipment	(1,505)	(807)	(2,048)	(1,077)
Operating (loss) income	(5,729)	23,989	(18,564)	(12,452)
Other (income) expense
Interest income	(1,173)	(1,164)	(2,694)	(2,215)
Interest expense	3,203	2,694	5,638	5,437
Equity in income of affiliates	(3,534)	(1,259)	(3,758)	(2,175)
Other income, net	(940)	(642)	(672)	(1,512)
Total other income	2,444	371	1,486	465
(Loss) income before provision for (benefit from) income taxes	(3,285)	24,360	(17,078)	(11,987)
Provision for (benefit from) income taxes	2,796	8,088	(1,335)	(4,408)
Net (loss) income	(6,081)	16,272	(15,743)	(7,579)
Amount attributable to non-controlling interests	(2,304)	(2,139)	(4,065)	(2,078)
Net (loss) income attributable to Granite Construction Incorporated	$ (8,385)	$ 14,133	$ (19,808)	$ (9,657)
Net (loss) income per share attributable to common shareholders (see Note 15)
Basic	$ (0.20)	$ 0.35	$ (0.49)	$ (0.24)
Diluted	$ (0.20)	$ 0.35	$ (0.49)	$ (0.24)
Weighted average shares of common stock
Basic	41,044	39,827	40,074	39,738
Diluted	41,044	40,393	40,074	39,738
Dividends per common share	$ 0.13	$ 0.13	$ 0.26	$ 0.26
Construction [Member]
Revenue
Total revenue	$ 432,225	$ 429,269	$ 701,468	$ 656,118
Cost of revenue
Total cost of revenue	370,674	368,369	601,521	567,889
Large Project Construction [Member]
Revenue
Total revenue	273,946	254,463	522,360	461,496
Cost of revenue
Total cost of revenue	272,608	253,974	500,656	458,452
Construction Materials [Member]
Revenue
Total revenue	100,948	79,181	146,670	113,699
Cost of revenue
Total cost of revenue	$ 83,468	$ 66,000	$ 131,669	$ 105,276