Property and Equipment - Gross Components of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,544,857	$ 2,241,444
Vessels [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,944,753	1,657,448
Vessels [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Vessels [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	30 years
ROVs, trenchers and ROVDrills [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 311,971	310,841
Estimated Useful Life	10 years
Machinery, equipment, buildings and leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 288,133	$ 273,155
Machinery, equipment, buildings and leasehold improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Machinery, equipment, buildings and leasehold improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	30 years