Note 11 - Investments in Affiliates - Summarized Balance Sheet Information for Equity Method Investments (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Current assets		$ 1,376,941	$ 1,493,291	$ 1,377,420	$ 1,209,845	$ 1,340,504	$ 1,515,028	$ 1,324,319	$ 1,052,354
Total assets		2,502,088	2,612,660	2,524,617	2,358,603	2,427,150	2,621,073	2,529,035	1,719,430
Current liabilities		842,056	$ 876,526	$ 839,722	$ 675,777	737,437	$ 873,412	$ 931,305	$ 614,117
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Current assets		122,348				141,930
Noncurrent assets		165,331				170,172
Total assets		287,679				312,102
Current liabilities		48,322				55,816
Long-term liabilities (1)	[1]	61,078				63,098
Total liabilities		109,400				118,914
Net assets		178,279				193,188
Granite’s share of net assets		$ 84,176				$ 84,354

[1] The balance primarily relates to debt associated with our real estate investments.