Company Overview (Details) $ in Thousands	1 Months Ended		9 Months Ended		12 Months Ended
	Feb. 29, 2016 USD ($)	Feb. 28, 2014 vessel	Sep. 30, 2016 USD ($) segment vessel	Sep. 30, 2015 USD ($)	Dec. 31, 2017
Segment Reporting Information [Line Items]
Number of reportable segments | segment			3
Sale of ownership interest for cash | $			$ 25,000	$ 0
Deepwater Gateway, L.L.C. [Member]
Segment Reporting Information [Line Items]
Sale of ownership interest for cash | $	$ 25,000
Robotics [Member]
Segment Reporting Information [Line Items]
Number of chartered vessels			3
Q5000 [Member]
Segment Reporting Information [Line Items]
Term of contract			5 years
Q5000 [Member] | Forecast [Member]
Segment Reporting Information [Line Items]
Minimum contracted vessel days					270 days
Monohull Vessels [Member]
Segment Reporting Information [Line Items]
Number of chartered vessels		2
Monohull Vessels [Member] | Well Intervention [Member]
Segment Reporting Information [Line Items]
Number of chartered vessels			2