Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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	$ 7,907		$ 28,927
Disposal Group Including Discontinued Operation Revenue	4,663	$ 8,592
Disposal Group, Including Discontinued Operation, Cost of Revenue	11,361	11,027
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	2,069	2,954
Disposal Group, Including Discontinued Operation, General and Administrative Expense	1,439	1,705
Disposal Group, Including Discontinued Operation, Interest Expense	39
Disposal Group, Including Discontinued Operation, Other Income		96
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	(10,245)	(6,998)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	33,788	0
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	(44,033)	(6,998)
Discontinued Operation, Tax Effect of Discontinued Operation	(2,327)	9
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(41,706)	(7,007)
Disposal Group, Including Discontinued Operation, Inventory	0		4,616
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		85,873
Disposal Group, Including Discontinued Operation, Assets, Other Assets	0		1,718
Disposal Group, Including Discontinued Operation, Assets	7,907	121,092	121,134
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	6,737		14,029
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	7,550		11,183
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		46,662
Disposal Group, Including Discontinued Operation, Liabilities	14,287		71,874
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	1,433		1,542
Disposal Group Including Discontinued Operation Revenue	186	231
Disposal Group, Including Discontinued Operation, Cost of Revenue	238	287
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	213	370
Disposal Group, Including Discontinued Operation, General and Administrative Expense	186	237
Disposal Group, Including Discontinued Operation, Interest Expense	0
Disposal Group, Including Discontinued Operation, Other Income		0
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	(451)	(663)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax
Disposal Group, Including Discontinued Operation, Inventory	0		0
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		0
Disposal Group, Including Discontinued Operation, Assets, Other Assets	0		44
Disposal Group, Including Discontinued Operation, Assets	1,433		1,586
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	228		87
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	2,222		2,278
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		46,662
Disposal Group, Including Discontinued Operation, Liabilities	2,450		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	6,474		27,385
Disposal Group Including Discontinued Operation Revenue	4,477	8,361
Disposal Group, Including Discontinued Operation, Cost of Revenue	11,123	10,740
Disposal Group, Including Discontinued Operation, Depreciation and Amortization	1,856	2,584
Disposal Group, Including Discontinued Operation, General and Administrative Expense	1,253	1,468
Disposal Group, Including Discontinued Operation, Interest Expense	39
Disposal Group, Including Discontinued Operation, Other Income		96
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	(9,794)	(6,335)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax
Disposal Group, Including Discontinued Operation, Inventory	0		4,616
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	0		85,873
Disposal Group, Including Discontinued Operation, Assets, Other Assets	0		1,674
Disposal Group, Including Discontinued Operation, Assets	6,474		119,548
Disposal Group, Including Discontinued Operation, Accounts Payable, Current	6,509		13,942
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current	5,328		8,905
Disposal Group, Including Discontinued Operation, Liabilities, Decommissioning and Asset Retirement Obligations	0		0
Disposal Group, Including Discontinued Operation, Liabilities	$ 11,837		$ 22,847