Note 10 - Construction Joint Ventures - Schedule of Unconsolidated Construction Joint Ventures Revenue and Costs (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Cost of revenue		$ 606,595	$ 612,128
Collaborative Arrangement [Member]
Revenue		79,722	83,702
Cost of revenue		79,336	95,717
Granite’s interest in gross profit (loss)		386	(12,015)
Collaborative Arrangement [Member] | Corporate Joint Venture [Member]
Revenue		232,042	62,030
Cost of revenue		248,070	228,460
Collaborative Arrangement [Member] | Co-venturer [Member] | Other Partners Interest in Partnerships [Member]
Revenue	[1]	152,320	(21,672)
Cost of revenue	[1]	$ 168,734	$ 132,743

[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.