Note 1 - Nature of Operations and Summary of Significant Accounting Policies - Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Affiliate credit loss impairment expense	$ 0	$ 400	$ 52,981
Trade Accounts Receivable [Member]
Balance	1,948	1,516	70
Affiliate credit loss impairment expense	414	838	1,283
Other	0	0	0
Write offs		(406)
Other	0	0	0
Acquisition of Sonatide joint venture	0
Balance	2,362	1,948	1,516
Trade Accounts Receivable [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance			163
Due from Affiliate [Member]
Balance	72,456	71,800	20,083
Affiliate credit loss impairment expense	0	400	52,981
Other	(1,080)	256	(1,264)
Write offs		0
Other	(1,080)	256	(1,264)
Acquisition of Sonatide joint venture	(59,678)
Balance	$ 11,698	$ 72,456	71,800
Due from Affiliate [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance			$ 0