Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue
Total revenue	$ 964,172	$ 915,771	$ 1,634,085	$ 1,551,698
Cost of revenue
Total cost of revenue	847,226	827,428	1,453,821	1,439,556
Gross profit	116,946	88,343	180,264	112,142
Selling, general and administrative expenses	74,069	78,023	149,797	151,239
Non-cash impairment charges (see Note 3)	0	0	0	24,413
Other costs (see Note 3)	5,953	13,659	81,788	18,824
Gain on sales of property and equipment, net (see Note 12)	(31,636)	(1,190)	(34,190)	(1,813)
Operating income (loss)	68,560	(2,149)	(17,131)	(80,521)
Other (income) expense
Interest income	(188)	(767)	(444)	(2,058)
Interest expense	5,507	6,549	10,888	11,543
Equity in income of affiliates, net	(6,231)	(2,016)	(8,039)	(2,062)
Other (income) expense, net	(1,894)	(3,160)	(3,124)	2,059
Total other (income) expense	(2,806)	606	(719)	9,482
Income (loss) before provision for (benefit from) income taxes	71,366	(2,755)	(16,412)	(90,003)
Provision for (benefit from) income taxes	15,619	(1,782)	(6,836)	(16,492)
Net income (loss)	55,747	(973)	(9,576)	(73,511)
Amount attributable to non-controlling interests	(1,286)	4,378	(2,158)	11,546
Net income (loss) attributable to Granite Construction Incorporated	$ 54,461	$ 3,405	$ (11,734)	$ (61,965)
Net income (loss) per share attributable to common shareholders (see Note 14)
Basic (in dollars per share)	$ 1.19	$ 0.07	$ (0.26)	$ (1.36)
Diluted (in dollars per share)	$ 1.14	$ 0.07	$ (0.26)	$ (1.36)
Weighted average shares of common stock
Basic (in shares)	45,798	45,620	45,748	45,570
Diluted (in shares)	47,798	46,281	45,748	45,570
Transportation [Member]
Revenue
Total revenue	$ 525,235	$ 535,101	$ 876,264	$ 886,002
Cost of revenue
Total cost of revenue	465,718	503,904	780,881	829,436
Water [Member]
Revenue
Total revenue	113,432	109,724	213,185	211,381
Cost of revenue
Total cost of revenue	102,869	97,145	194,056	189,455
Specialty [Member]
Revenue
Total revenue	200,271	174,914	355,945	307,953
Cost of revenue
Total cost of revenue	175,902	149,634	314,251	293,392
Materials [Member]
Revenue
Total revenue	125,234	96,032	188,691	146,362
Cost of revenue
Total cost of revenue	$ 102,737	$ 76,745	$ 164,633	$ 127,273