Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue
Total revenue	$ 1,088,110	$ 1,055,591	$ 2,497,451	$ 2,426,089
Cost of revenue
Total cost of revenue	996,678	911,100	2,417,945	2,144,946
Gross profit	91,432	144,491	79,506	281,143
Selling, general and administrative expenses	73,424	70,769	224,577	193,337
Acquisition and integration expenses	2,744	9,334	15,244	44,030
Gain on sales of property and equipment, net	(7,101)	(3,018)	(13,936)	(5,066)
Operating income (loss)	22,365	67,406	(146,379)	48,842
Other (income) expense
Interest income	(1,713)	(1,533)	(6,257)	(4,227)
Interest expense	4,839	4,452	13,011	10,090
Equity in income of affiliates	(6,275)	(1,769)	(10,159)	(5,527)
Other expense (income), net	127	(1,533)	(2,394)	(2,205)
Total other income	(3,022)	(383)	(5,799)	(1,869)
Income (loss) before provision for (benefit from) income taxes	25,387	67,789	(140,580)	50,711
Provision for (benefit from) income taxes	3,474	8,692	(37,451)	7,357
Net income (loss)	21,913	59,097	(103,129)	43,354
Amount attributable to non-controlling interests	(1,425)	(3,425)	(8,793)	(7,490)
Net income (loss) attributable to Granite Construction Incorporated	$ 20,488	$ 55,672	$ (111,922)	$ 35,864
Net income (loss) per share attributable to common shareholders
Basic (in dollars per share)	$ 0.44	$ 1.20	$ (2.39)	$ 0.84
Diluted (in dollars per share)	$ 0.43	$ 1.17	$ (2.39)	$ 0.84
Weighted average shares of common stock
Basic (in shares)	46,788	46,308	46,771	42,443
Diluted (in shares)	47,170	47,810	46,771	42,910
Transportation [Member]
Revenue
Total revenue	$ 598,646	$ 610,847	$ 1,340,834	$ 1,472,703
Cost of revenue
Total cost of revenue	585,013	539,871	1,405,830	1,334,302
Water [Member]
Revenue
Total revenue	135,908	124,292	347,994	215,951
Cost of revenue
Total cost of revenue	120,878	100,189	313,582	174,834
Specialty [Member]
Revenue
Total revenue	224,457	190,836	540,234	461,149
Cost of revenue
Total cost of revenue	186,158	162,737	464,858	395,838
Materials [Member]
Revenue
Total revenue	129,099	129,616	268,389	276,286
Cost of revenue
Total cost of revenue	$ 104,629	$ 108,303	$ 233,675	$ 239,972