Other Accrued Expenses Schedule of Other Accrued Expense (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Schedule of Other Accrued Expense [Line Items]
Document Period End Date	Mar. 31, 2019
Accrued Employee Benefits, Current	$ 10,188	$ 25,811
Asset Retirement Obligation, Current	28,798	25,598
Accrued Environmental Loss Contingencies, Current	3,554	3,038
Operating and Finance Lease Liability, Current	6,645	0
Other accrued expenses	68,836	75,133
Current Liabilities
Schedule of Other Accrued Expense [Line Items]
Other Accrued Liabilities	19,651	20,686
Non Current Liabilities
Schedule of Other Accrued Expense [Line Items]
Other Accrued Liabilities	$ 3,988	$ 8,644