Note 16 - Weighted Average Shares Outstanding and Net Income (Loss) Per Share - Reconciliation of the Weighted Average Shares Outstanding in Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net loss from continuing operations allocated to common shareholders	$ (19,035)	$ (63,273)
Net income (loss) attributable to Granite Construction Incorporated from discontinued operations	6,096	(2,922)
Net loss allocated to common shareholders	$ (12,939)	$ (66,195)
Weighted average common shares outstanding, basic (in shares)	45,730	45,697
Weighted average common shares outstanding, diluted (in shares)	45,730	45,697
Basic continuing operations per share (in dollars per share)	$ (0.42)	$ (1.38)
Basic discontinued operations per share (in dollars per share)	0.13	(0.07)
Basic loss per share (in dollars per share)	(0.29)	(1.45)
Diluted continuing operations per share (in dollars per share)	(0.42)	(1.38)
Diluted loss per share (in dollars per share)	$ (0.29)	$ (1.45)