Note 13 - Segment and Geographic Distribution of Operations - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue	$ 92,401	$ 86,467	$ 265,858	$ 305,179
Corporate expenses	(113,965)	(111,643)	(333,882)	(466,633)
Long-lived asset impairments	(2,167)	(1,945)	(2,167)	(67,634)
Affiliate credit loss impairment (expense) credit	0	0	1,000	(53,581)
Affiliate guarantee obligation	0	0	0	(2,000)
Gain (loss) on asset dispositions, net	(74)	520	(2,954)	7,511
Operating loss	(21,564)	(25,176)	(68,024)	(161,454)
Depreciation and amortization	27,980	30,777	86,256	86,028
Additions to properties and equipment	722	607	2,583	4,682
Operating Segments [Member]
Revenue	92,401	86,467	265,858	305,179
Gross profit	(8,661)	(15,313)	(36,666)	(18,360)
Corporate, Non-Segment [Member]
Corporate expenses	(10,662)	(8,438)	(27,237)	(27,390)
Depreciation and amortization	877	791	2,504	2,535
Additions to properties and equipment	477	636	1,233	1,924
Americas [Member] | Operating Segments [Member]
Depreciation and amortization	7,290	8,076	22,679	23,645
Reductions to properties and equipment	0	(10)	0	(10)
Middle East and Asia Pacific [Member] | Operating Segments [Member]
Depreciation and amortization	6,370	6,332	19,771	17,504
Reductions to properties and equipment	0		(42)
Additions to properties and equipment		5		1,188
Europe and Mediterranean [Member] | Operating Segments [Member]
Depreciation and amortization	6,834	8,248	21,543	21,860
Reductions to properties and equipment		(13)
Additions to properties and equipment	146		739	913
West Africa [Member] | Operating Segments [Member]
Depreciation and amortization	6,609	7,330	19,759	20,484
Reductions to properties and equipment		(11)
Additions to properties and equipment	99		653	667
Vessel [Member]
Revenue	91,634	85,395	261,141	298,344
Vessel [Member] | Americas [Member] | Operating Segments [Member]
Revenue	24,564	28,705	74,269	94,608
Gross profit	(1,770)	107	(8,361)	3,448
Vessel [Member] | Middle East and Asia Pacific [Member] | Operating Segments [Member]
Revenue	25,633	23,280	75,675	72,091
Gross profit	(713)	(2,222)	(2,300)	(2,479)
Vessel [Member] | Europe and Mediterranean [Member] | Operating Segments [Member]
Revenue	21,197	17,716	58,413	67,827
Gross profit	(2,866)	(3,883)	(12,873)	(4,086)
Vessel [Member] | West Africa [Member] | Operating Segments [Member]
Revenue	20,240	15,694	52,784	63,818
Gross profit	(3,724)	(10,168)	(15,846)	(19,015)
Product and Service, Other [Member]
Revenue	767	1,072	4,717	6,835
Product and Service, Other [Member] | Operating Segments [Member]
Revenue	767	1,072	4,717	6,835
Gross profit	$ 412	$ 853	$ 2,714	$ 3,772