Note 7 - Other Costs (Details Textual) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Police Retirement System of St. Louis v. Granite Construction Incorporated, et al. [Member]
Litigation Settlement, Expense	$ 66

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

No definition available.

Name:	us-gaap_LitigationSettlementExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration