Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Write off of Amortization of Leased Assets [Line Items]
Non-cash provision for leased items no longer in use	$ 12,589	$ 0	$ 12,589	$ 0
Onshore facilities and transportation
Write off of Amortization of Leased Assets [Line Items]
Non-cash provision for leased items no longer in use	12,600
Accrued Liabilities
Write off of Amortization of Leased Assets [Line Items]
Loss contingency, accrual, current	$ 4,100		$ 4,100