Note 16 - Weighted Average Shares Outstanding and Net Income (Loss) Per Share - Reconciliation of the Weighted Average Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net income (loss) from continuing operations allocated to common shareholders	$ (2,370)	$ 24,859	$ (21,405)	$ (38,414)
Net income attributable to Granite Construction Incorporated from discontinued operations	19,521	29,602	25,617	26,680
Net income (loss) allocated to common shareholders	$ 17,151	$ 54,461	$ 4,212	$ (11,734)
Weighted average common shares outstanding, basic (in shares)	44,534	45,798	45,128	45,748
Dilutive effect of RSUs and convertible notes (in shares)	0	454	0	0
Dilutive effect of 2.75% Convertible Notes (in shares)	0	1,546	0	0
Weighted average common shares outstanding, diluted (in shares)	44,534	47,798	45,128	45,748
Net income (loss) from continuing operations per share (in dollars per share)	$ (0.05)	$ 0.54	$ (0.47)	$ (0.84)
Net income from discontinued operations per share (in dollars per share)	0.44	0.65	0.57	0.58
Net income (loss) per share (in dollars per share)	0.39	1.19	0.10	(0.26)
Net income (loss) from continuing operations per share (in dollars per share)	(0.05)	0.52	(0.47)	(0.84)
Net income from discontinued operations per share (in dollars per share)	0.44	0.62	0.57	0.58
Net income (loss) per share (in dollars per share)	$ 0.39	$ 1.14	$ 0.10	$ (0.26)