Note 10 - Construction Joint Ventures - Schedule of Unconsolidated Construction Joint Ventures Revenue and Costs (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cost of revenue		$ 942,194	$ 939,192	$ 2,396,015	$ 2,378,748
Collaborative Arrangement [Member]
Revenue		81,281	87,701	247,904	268,225
Cost of revenue		80,325	95,844	240,114	306,756
Granite’s interest in gross profit (loss)		956	(8,143)	7,790	(38,531)
Collaborative Arrangement [Member] | Corporate Joint Venture [Member]
Revenue		194,486	293,733	690,086	740,224
Cost of revenue		203,786	299,776	701,350	884,991
Collaborative Arrangement [Member] | Co-venturer [Member] | Other Partners Interest in Partnerships [Member]
Revenue	[1]	113,205	206,032	442,182	471,999
Cost of revenue	[1]	$ 123,461	$ 203,932	$ 461,236	$ 578,235

[1] Partners' interest and adjustments includes amounts to reconcile total revenue and total cost of revenue as reported by our partners to Granite's interest adjusted to reflect our accounting policies and estimates primarily related to contract forecast differences.