Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net	$ (1,288)		$ (1,288)		$ (28,927)
Disposal Group Including Discontinued Operation Revenue	0	$ 32,688	4,674	$ 69,717
Disposal Group, Including Discontinued Operation, Cost of Revenue	125	28,576	11,152	67,849
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	0	3,258	2,085	9,047
Disposal Group, Including Discontinued Operation, General and Administrative Expense	192	1,522	1,916	4,996
Disposal Group, Including Discontinued Operation, Other Expense				1,852
Disposal Group, Including Discontinued Operation, Other Income	(1,113)	(206)	(1,035)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	796	(462)	(9,444)	(14,027)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax			(33,813)	0
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax			(43,257)	(14,027)
Discontinued Operation, Tax Effect of Discontinued Operation	0	19	(2,326)	114
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	796	(481)	(40,931)	(14,141)
Disposal Group, Including Discontinued Operation, Inventory	0		0		4,616
Disposal Group, Including Discontinued Operation, Other Assets, Current	13		13		1,336
Disposal Group, Including Discontinued Operation, Assets, Current	(1,301)		(1,301)		(34,879)
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0		85,873
Disposal Group, Including Discontinued Operation, Assets, Other Assets	0		0		382
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	0		0		86,255
Disposal Group, Including Discontinued Operation, Assets	(1,301)	(121,134)	(1,301)	(121,134)	(121,134)
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	0		0		14,029
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	3,570		3,570		11,182
Disposal Group, Including Discontinued Operation, Liabilities, Current Decommissioning and Asset Retirement Obligations	0		0		477
Disposal Group, Including Discontinued Operation, Liabilities, Current	3,570		3,570		25,688
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0		46,185
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent	0		0		2,040
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0		0		48,225
Disposal Group, Including Discontinued Operation, Liabilities	3,570		3,570		73,913
Maritech [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net	(1,341)		(1,341)		(1,542)
Disposal Group Including Discontinued Operation Revenue	0	21	187	427
Disposal Group, Including Discontinued Operation, Cost of Revenue	0	386	139	987
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	0	372	212	1,115
Disposal Group, Including Discontinued Operation, General and Administrative Expense	0	177	187	588
Disposal Group, Including Discontinued Operation, Other Income	0	0	0	(565)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	0	(914)	(351)	(1,698)
Disposal Group, Including Discontinued Operation, Inventory	0		0		0
Disposal Group, Including Discontinued Operation, Other Assets, Current	0		0		44
Disposal Group, Including Discontinued Operation, Assets, Current	(1,341)		(1,341)		(1,586)
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0		0
Disposal Group, Including Discontinued Operation, Assets, Other Assets	0		0		0
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	0		0		0
Disposal Group, Including Discontinued Operation, Assets	(1,341)		(1,341)		(1,586)
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	0		0		87
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	2,075		2,075		2,278
Disposal Group, Including Discontinued Operation, Liabilities, Current Decommissioning and Asset Retirement Obligations	0		0		477
Disposal Group, Including Discontinued Operation, Liabilities, Current	2,075		2,075		2,842
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0		46,185
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent	0		0		0
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0		0		46,185
Disposal Group, Including Discontinued Operation, Liabilities	2,075		2,075		49,027
Offshore Services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net	(53)		(53)		(27,385)
Disposal Group Including Discontinued Operation Revenue	0	32,667	4,487	69,290
Disposal Group, Including Discontinued Operation, Cost of Revenue	125	28,190	11,013	66,862
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	0	2,886	1,873	7,932
Disposal Group, Including Discontinued Operation, General and Administrative Expense	192	1,345	1,729	4,408
Disposal Group, Including Discontinued Operation, Other Expense				2,417
Disposal Group, Including Discontinued Operation, Other Income	(1,113)	(206)	(1,035)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	796	$ 452	(9,093)	$ (12,329)
Disposal Group, Including Discontinued Operation, Inventory	0		0		4,616
Disposal Group, Including Discontinued Operation, Other Assets, Current	13		13		1,292
Disposal Group, Including Discontinued Operation, Assets, Current	(40)		(40)		(33,293)
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0		85,873
Disposal Group, Including Discontinued Operation, Assets, Other Assets	0		0		382
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	0		0		86,255
Disposal Group, Including Discontinued Operation, Assets	(40)		(40)		(119,548)
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	0		0		13,942
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	1,495		1,495		8,904
Disposal Group, Including Discontinued Operation, Liabilities, Current Decommissioning and Asset Retirement Obligations	0		0		0
Disposal Group, Including Discontinued Operation, Liabilities, Current	1,495		1,495		22,846
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0		0
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent	0		0		2,040
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0		0		2,040
Disposal Group, Including Discontinued Operation, Liabilities	$ 1,495		$ 1,495		$ 24,886