Note 5 - Investment in Unconsolidated Affiliates (Details Textual) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Apr. 22, 2021	Jun. 22, 2020	Jun. 30, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2022
Due from Affiliate, Current				$ 0	$ 70,134
Accounts Receivable, Credit Loss Expense (Reversal)				0	400	$ 52,981
Due to Affiliate, Current				0	61,555
Revenue from Contract with Customer, Excluding Assessed Tax, Total				647,684	371,033	397,038
Sonatide Marine Ltd [Member]
Dividends, Total			$ 35,000
Sonatide Marine Ltd [Member]
Business Acquisition, Percentage of Voting Interests Acquired							51.00%
Sonatide Marine Ltd [Member]
Due from Affiliate, Current					49,000
Proceeds from Dividends Received		$ 17,200
Accounts Receivable, Credit Loss Expense (Reversal)				$ (0)	400	40,900
Due to Affiliate, Current					40,400
Sonatide Marine Ltd [Member] | ANGOLA
Revenue from Contract with Customer, Excluding Assessed Tax, Total					$ 43,200	$ 45,300
Sales Revenue Services Percentage					11.90%	11.70%
Number of Vessels					24	23
Number of Stacked Vessels					5	6
Sonatide Marine Ltd [Member] | Sonangol [Member]
Proceeds from Dividends Received		$ 17,800
DTDW [Member]
Accounts Receivable, Credit Loss Expense (Reversal)						$ 12,100
Number of Vessels					1
Equity Method Investment, Ownership Percentage					40.00%
Equity Method Investment, Ownership Percentage by Other Owners					60.00%
Secured Long-term Debt, Noncurrent						4,700
Guarantor Obligations, Maximum Exposure, Undiscounted						$ 2,000
Payments To Settle Debt Guarantee	$ 2,000