Supplemental Cash Flow Supplemental Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Line Items]
Interest Paid, Excluding Capitalized Interest, Operating Activities	$ 57,439	$ 55,586	$ 69,880
Income Taxes Paid, Net	(1,167)	(6,719)	(13,925)
Capital Expenditures Incurred but Not yet Paid	(68,246)	36,328	50,761
Noncash Change In Asset Retirement Obligation	29,533	37,136	839
Operating Lease, Payments	5,301
Operating Cash Flow from Financing Leases	253
Finance Lease, Principal Payments	1,952	1,495	1,168
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	1,428
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 2,323
Not Restated [Domain]
Supplemental Cash Flow Elements [Line Items]
Operating Lease, Payments		0	0
Operating Cash Flow from Financing Leases		0	0
Finance Lease, Principal Payments		0	0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		0	0
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability		$ 0	$ 0