Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017
Write off of Amortization of Leased Assets [Line Items]
Non-cash provision for leased items no longer in use	$ 186		$ 0
Loss Contingency Accrual	9,300
Accrued Liabilities
Write off of Amortization of Leased Assets [Line Items]
Loss contingency, accrual, current	$ 3,900
Onshore Facilities & Transportation
Write off of Amortization of Leased Assets [Line Items]
Non-cash provision for leased items no longer in use		$ 12,600