Note 11 - Investments in Affiliates - Summarized Balance Sheet Information for Equity Method Investments (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Current assets		$ 1,450,741	$ 1,455,246	$ 1,301,064
Total assets		2,373,684	2,379,996	2,384,375
Current liabilities		1,000,135	943,256	809,562
Granite’s share of net assets		75,159	75,287	73,249
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Current assets		136,672	133,882	112,426
Noncurrent assets		161,416	164,620	163,452
Total assets		298,088	298,502	275,878
Current liabilities		55,971	52,583	45,617
Long-term liabilities (1)	[1]	59,718	66,108	57,182
Total liabilities		115,689	118,691	102,799
Net assets		182,399	179,811	173,079
Granite’s share of net assets		$ 75,159	$ 75,287	$ 73,249

[1] The balance primarily related to local bank debt for equipment purchases and working capital in our foreign affiliates and debt associated with our real estate investments.