Note 4 - Revisions in Estimates - Summary of Impact of Revisions in Estimates to Gross Profit (Details) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) $ / shares	Jun. 30, 2021 USD ($) $ / shares	Jun. 30, 2022 USD ($) $ / shares	Jun. 30, 2021 USD ($) $ / shares
Range of reduction in gross profit from each project, net	$ 78,480	$ 98,232	$ 128,255	$ 151,944
Decrease to project profitability	(404)	33,855	(21,652)	(50,303)
Net income (loss)	16,568	55,747	6,747	(9,576)
Decrease to net income/increase to net loss attributable to Granite Construction Incorporated from continuing operations	$ 17,151	$ 54,461	$ 4,212	$ (11,734)
Diluted earnings (loss) per share (in dollars per share) | $ / shares	$ 0.39	$ 1.14	$ 0.10	$ (0.26)
Estimated Cost Recovery of Customer Affirmative Claims and Back Charges [Member]
Number of projects with downward estimate changes	4	0	5	2
Range of reduction in gross profit from each project, net		$ 0
Decrease to project profitability	$ 25,200	0	$ 35,600	$ 11,400
Net income (loss)	19,300	0	27,300	8,900
Amounts attributable to non-controlling interests	3,000	0	3,000	2,600
Decrease to net income/increase to net loss attributable to Granite Construction Incorporated from continuing operations	$ 16,300	$ 0	$ 24,200	$ 6,300
Diluted earnings (loss) per share (in dollars per share) | $ / shares	$ 0.37	$ 0	$ 0.54	$ 0.14
Estimated Cost Recovery of Customer Affirmative Claims and Back Charges [Member] | Minimum [Member]
Range of reduction in gross profit from each project, net	$ 5,700	$ 5,600	$ 5,300
Estimated Cost Recovery of Customer Affirmative Claims and Back Charges [Member] | Maximum [Member]
Range of reduction in gross profit from each project, net	$ 7,600		$ 10,600	$ 6,100