Note 10 - Construction Joint Ventures - Schedule of Unconsolidated Construction Joint Ventures Revenue and Costs (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cost of revenue		$ 847,226	$ 827,428	$ 1,453,821	$ 1,439,556
Collaborative Arrangement [Member]
Revenue		86,901	96,822	166,623	180,524
Cost of revenue		80,453	115,195	159,789	210,912
Granite’s interest in gross profit (loss)		6,448	(18,373)	6,834	(30,388)
Collaborative Arrangement [Member] | Corporate Joint Venture [Member]
Revenue		263,558	384,461	495,600	446,491
Cost of revenue		249,494	356,755	497,564	585,215
Collaborative Arrangement [Member] | Co-venturer [Member] | Other Partners Interest in Partnerships [Member]
Revenue	[1]	176,657	287,639	328,977	265,967
Cost of revenue	[1]	$ 169,041	$ 241,560	$ 337,775	$ 374,303

[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.