Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021		Mar. 31, 2020		Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenues	$ 36,512		$ 35,667
Direct Costs and Expenses	26,307		20,735
Direct Vessel Profit	10,205		14,932
Lease expense	1,078		3,325
Administrative and general	8,611		9,394
Depreciation and amortization	14,798		13,362
Other Costs and Expenses	24,487		26,081
Loss on Asset Dispositions and Impairments	(2,273)		(12,572)
Operating Loss	(16,555)		(23,721)
Historical cost	1,000,430		857,118		$ 1,012,873
Accumulated depreciation	(297,792)		(264,365)		(291,538)
Property and equipment	702,638		592,753		$ 721,335
Total Assets	831,638	[1]	781,951	[2]
Time Charter
Segment Reporting Information [Line Items]
Operating Revenues	34,290		33,549
Bareboat Charter
Segment Reporting Information [Line Items]
Operating Revenues	729		724
Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues	1,493		1,394
Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses	13,418		11,186
Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses	3,840		3,840
Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses	2,217		1,365
Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses	1,958		840
Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses	2,202		1,841
Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses	2,672		1,663
UNITED STATES
Segment Reporting Information [Line Items]
Operating Revenues	2,764		5,741
Direct Costs and Expenses	4,076		5,340
Direct Vessel Profit	(1,312)		401
Lease expense	664		2,138
Depreciation and amortization	4,164		5,358
Historical cost	214,575		256,059
Accumulated depreciation	(128,841)		(120,599)
Property and equipment	85,734		135,460
Total Assets	125,479	[1]	191,611	[2]
UNITED STATES | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues	1,489		4,375
UNITED STATES | Bareboat Charter
Segment Reporting Information [Line Items]
Operating Revenues	729		724
UNITED STATES | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues	546		642
UNITED STATES | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses	1,744		2,928
UNITED STATES | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses	654		617
UNITED STATES | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses	875		1,057
UNITED STATES | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses	527		135
UNITED STATES | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses	199		524
UNITED STATES | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses	77		79
Africa and Europe, Continuing Operations
Segment Reporting Information [Line Items]
Operating Revenues	10,233	[3]	14,194	[4]
Direct Costs and Expenses	6,299	[3]	6,235	[4]
Direct Vessel Profit	3,934	[3]	7,959	[4]
Lease expense	356	[3]	1,133	[4]
Depreciation and amortization	3,307	[3]	3,315	[4]
Historical cost	240,032	[3]	244,984	[4]
Accumulated depreciation	(68,254)	[3]	(58,666)	[4]
Property and equipment	171,778	[3]	186,318	[4]
Total Assets	189,370	[1],[3]	210,890	[2],[4]
Africa and Europe, Continuing Operations | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues	10,502	[3]	14,011	[4]
Africa and Europe, Continuing Operations | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues	(269)	[3]	183	[4]
Africa and Europe, Continuing Operations | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses	3,220	[3]	3,232	[4]
Africa and Europe, Continuing Operations | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses	1,191	[3]	1,585	[4]
Africa and Europe, Continuing Operations | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses	304	[3]	8	[4]
Africa and Europe, Continuing Operations | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses	433	[3]	297	[4]
Africa and Europe, Continuing Operations | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses	572	[3]	517	[4]
Africa and Europe, Continuing Operations | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses	579	[3]	596	[4]
Middle East and Asia
Segment Reporting Information [Line Items]
Operating Revenues	12,935		12,187
Direct Costs and Expenses	9,582		7,158
Direct Vessel Profit	3,353		5,029
Lease expense	22		45
Depreciation and amortization	4,710		3,790
Historical cost	374,979		281,767
Accumulated depreciation	(76,675)		(67,829)
Property and equipment	298,304		213,938
Total Assets	301,381	[1]	245,279	[2]
Middle East and Asia | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues	12,575		11,767
Middle East and Asia | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues	360		420
Middle East and Asia | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses	5,208		3,811
Middle East and Asia | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses	903		1,246
Middle East and Asia | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses	1,066		414
Middle East and Asia | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses	702		339
Middle East and Asia | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses	559		665
Middle East and Asia | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses	1,144		683
Latin America
Segment Reporting Information [Line Items]
Operating Revenues	10,580		3,545
Direct Costs and Expenses	6,350		2,002
Direct Vessel Profit	4,230		1,543
Lease expense	36		9
Depreciation and amortization	2,617		899
Historical cost	170,844		74,308
Accumulated depreciation	(24,022)		(17,271)
Property and equipment	146,822		57,037
Total Assets	215,408	[1]	134,171	[2]
Latin America | Time Charter
Segment Reporting Information [Line Items]
Operating Revenues	9,724		3,396
Latin America | Other Marine Services
Segment Reporting Information [Line Items]
Operating Revenues	856		149
Latin America | Personnel
Segment Reporting Information [Line Items]
Direct Costs and Expenses	3,246		1,215
Latin America | Repairs and Maintenance
Segment Reporting Information [Line Items]
Direct Costs and Expenses	1,092		392
Latin America | Drydocking
Segment Reporting Information [Line Items]
Direct Costs and Expenses	(28)		(114)
Latin America | Insurance and Loss Reserves
Segment Reporting Information [Line Items]
Direct Costs and Expenses	296		69
Latin America | Fuel, Lubes and Supplies
Segment Reporting Information [Line Items]
Direct Costs and Expenses	872		135
Latin America | Other Direct Costs and Expenses
Segment Reporting Information [Line Items]
Direct Costs and Expenses	$ 872		$ 305

[1] Total assets by region does not include corporate assets of $142.2 million as of March 31, 2021

[2] Total assets by region does not include corporate assets of $142.0 million, and $42.5 million of discontinued operations as of March 31, 2020

[3] In prior periods Africa and Europe were reported as separate segments. Due to the sale of Windcat Workboats, the Company’s European operations are no longer analyzed by the chief operating decision maker on a standalone basis but rather as part of the Africa segment. As a result, for purposes of segment reporting European operations are now consolidated with Africa and reported as a consolidated segment and prior period information has been conformed to the new consolidated reporting segment.

[4] In prior periods Africa and Europe were reported as separate segments. Due to the sale of Windcat Workboats, the Company’s European operations are no longer analyzed by the chief operating decision maker on a standalone basis but rather as part of the Africa segment.  As a result, for purposes of segment reporting European operations are now consolidated with Africa and reported as a consolidated segment and prior period information has been conformed to the new consolidated reporting segment.