Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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	$ 1,502		$ 1,502		$ 28,927
Disposal Group Including Discontinued Operation Revenue	10	$ 28,437	4,674	$ 37,029
Disposal Group, Including Discontinued Operation, Cost of Revenue	(333)	28,247	11,027	39,273
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	0	2,836	2,085	5,789
Disposal Group, Including Discontinued Operation, General and Administrative Expense	284	1,768	1,724	3,474
Disposal Group, Including Discontinued Operation, Interest Expense	55	2,153
Disposal Group, Including Discontinued Operation, Other Expense			78	2,058
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	4	(6,567)	(10,240)	(13,565)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	(25)	0	(33,813)	0
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	(21)	(6,567)	(44,053)	(13,565)
Discontinued Operation, Tax Effect of Discontinued Operation	0	86	(2,326)	95
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(21)	(6,653)	(41,727)	(13,660)
Disposal Group, Including Discontinued Operation, Inventory	0		0		4,616
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0		85,873
Disposal Group, Including Discontinued Operation, Assets, Other Assets	36		36		1,718
Disposal Group, Including Discontinued Operation, Assets	1,538	121,134	1,538	121,134	121,134
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	1,676		1,676		14,029
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	6,667		6,667		13,222
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0		46,662
Disposal Group, Including Discontinued Operation, Liabilities	8,343		8,343		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	175	187	406
Disposal Group, Including Discontinued Operation, Cost of Revenue	(98)	314	139	601
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	0	373	212	743
Disposal Group, Including Discontinued Operation, General and Administrative Expense	0	174	187	411
Disposal Group, Including Discontinued Operation, Interest Expense	0
Disposal Group, Including Discontinued Operation, Other Expense			0
Disposal Group, Including Discontinued Operation, Other Income		(565)		(565)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	98	(121)	(351)	(784)
Disposal Group, Including Discontinued Operation, Inventory	0		0		0
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0		0
Disposal Group, Including Discontinued Operation, Assets, Other Assets	(18)		(18)		44
Disposal Group, Including Discontinued Operation, Assets	1,323		1,323		1,586
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	0		0		87
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	2,059		2,059		2,278
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0		46,662
Disposal Group, Including Discontinued Operation, Liabilities	2,059		2,059		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	161		161		27,385
Disposal Group Including Discontinued Operation Revenue	10	28,262	4,487	36,623
Disposal Group, Including Discontinued Operation, Cost of Revenue	(235)	27,933	10,888	38,672
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	0	2,463	1,873	5,046
Disposal Group, Including Discontinued Operation, General and Administrative Expense	284	1,594	1,537	3,063
Disposal Group, Including Discontinued Operation, Interest Expense	55	2,718
Disposal Group, Including Discontinued Operation, Other Expense			78	2,623
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	(94)	$ (6,446)	(9,889)	$ (12,781)
Disposal Group, Including Discontinued Operation, Inventory	0		0		4,616
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0		85,873
Disposal Group, Including Discontinued Operation, Assets, Other Assets	54		54		1,674
Disposal Group, Including Discontinued Operation, Assets	215		215		119,548
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	1,676		1,676		13,942
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	4,608		4,608		10,944
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0		0
Disposal Group, Including Discontinued Operation, Liabilities	$ 6,284		$ 6,284		$ 24,886