Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue
Total revenue	$ 1,062,129	$ 1,065,189	$ 2,696,214	$ 2,616,887
Cost of revenue
Total cost of revenue	942,194	939,192	2,396,015	2,378,748
Gross profit	119,935	125,997	300,199	238,139
Selling, general and administrative expenses	77,603	72,889	227,400	224,128
Non-cash impairment charges (see Note 3)	0	132,277	0	156,690
Other costs (see Note 3)	3,759	9,689	85,547	28,513
Gain on sales of property and equipment, net (see Note 12)	(5,159)	(3,057)	(39,349)	(4,870)
Operating income (loss)	43,732	(85,801)	26,601	(166,322)
Other (income) expense
Interest income	(293)	(755)	(737)	(2,813)
Interest expense	5,131	6,359	16,019	17,902
Equity in income of affiliates, net	(2,539)	(2,353)	(10,578)	(4,415)
Other expense (income), net	106	(1,967)	(3,018)	92
Total other expense, net	2,405	1,284	1,686	10,766
Income (loss) before provision for (benefit from) income taxes	41,327	(87,085)	24,915	(177,088)
Provision for (benefit from) income taxes	8,904	11,272	2,068	(5,220)
Net income (loss)	32,423	(98,357)	22,847	(171,868)
Amount attributable to non-controlling interests	2,620	7,195	462	18,741
Net income (loss) attributable to Granite Construction Incorporated	$ 35,043	$ (91,162)	$ 23,309	$ (153,127)
Net income (loss) per share attributable to common shareholders (see Note 14)
Basic (in dollars per share)	$ 0.76	$ (2.00)	$ 0.51	$ (3.36)
Diluted (in dollars per share)	$ 0.73	$ (2.00)	$ 0.49	$ (3.36)
Weighted average shares of common stock
Basic (in shares)	45,821	45,654	45,773	45,598
Diluted (in shares)	47,906	45,654	47,522	45,598
Transportation [Member]
Revenue
Total revenue	$ 568,186	$ 623,999	$ 1,444,450	$ 1,510,001
Cost of revenue
Total cost of revenue	509,683	569,677	1,290,564	1,399,113
Water [Member]
Revenue
Total revenue	121,968	106,599	335,153	317,980
Cost of revenue
Total cost of revenue	112,092	94,042	306,148	283,497
Specialty [Member]
Revenue
Total revenue	234,300	205,134	590,245	513,087
Cost of revenue
Total cost of revenue	203,442	171,842	517,693	465,234
Materials [Member]
Revenue
Total revenue	137,675	129,457	326,366	275,819
Cost of revenue
Total cost of revenue	$ 116,977	$ 103,631	$ 281,610	$ 230,904