Note 22 - Unaudited Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 683,196	$ 925,854	$ 834,671	$ 566,332	$ 830,390	$ 955,761	$ 811,866	$ 530,862	$ 3,010,053	$ 3,128,879	$ 2,914,877
Range of increase in gross profit from each project, net	$ 51,652	$ 101,960	$ 98,232	$ 53,712	$ 93,319	$ 113,015	$ 81,048	$ 17,271	305,556	304,653	189,785
As a percent of revenue	7.60%	11.00%	11.80%	9.50%	11.20%	11.80%	10.00%	3.30%
Net income (loss) from continuing operations	$ (406)	$ 28,403	$ 26,145	$ (62,401)	$ 2,513	$ 32,665	$ 3,645	$ (40,605)	(8,259)	(1,782)	(27,936)
Net income (loss) from discontinued operations	(20,027)	4,020	29,602	(2,922)	3,174	(131,022)	(4,618)	(31,933)	10,673	(164,399)	(28,766)
Net income (loss)	(20,433)	32,423	55,747	(65,323)	5,687	(98,357)	(973)	(72,538)	2,414	(166,181)	(56,702)
Net income (loss) from continuing operations allocated to common shareholders	6,814	31,023	24,859	(63,273)	4,836	39,860	8,023	(33,437)	(577)	19,282	(31,425)
Net income (loss) attributable to Granite	$ (13,213)	$ 35,043	$ 54,461	$ (66,195)	$ 8,010	$ (91,162)	$ 3,405	$ (65,370)	$ 10,096	$ (145,117)	$ (60,191)
Basic continuing operations per share (in dollars per share)	$ 0.15	$ 0.68	$ 0.54	$ (1.38)	$ 0.11	$ 0.87	$ 0.18	$ (0.73)	$ (0.01)	$ 0.42	$ (0.67)
Basic discontinued operations per share (in dollars per share)	(0.44)	0.08	0.65	(0.07)	0.07	(2.87)	(0.11)	(0.71)	0.23	(3.60)	(0.62)
Basic earnings per share (in dollars per share)	(0.29)	0.76	1.19	(1.45)	0.18	(2.00)	0.07	(1.44)	0.22	(3.18)	(1.29)
Diluted continuing operations per share (in dollars per share)	0.14	0.65	0.52	(1.38)	0.10	0.86	0.17	(0.73)	(0.01)	0.42	(0.67)
Diluted discontinued operations per share (in dollars per share)	(0.42)	0.08	0.62	(0.07)	0.07	(2.83)	(0.10)	(0.71)	0.23	(3.56)	(0.62)
Diluted earnings per share (in dollars per share)	$ (0.28)	$ 0.73	$ 1.14	$ (1.45)	$ 0.17	$ (1.97)	$ 0.07	$ (1.44)	$ 0.22	$ (3.14)	$ (1.29)