Supplemental Cash Flow Information (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Supplemental Cash Flow Elements [Line Items]
Interest, net of capitalized interest	$ 9,043	$ 16,915
Income taxes	(1,388)	(204)
Capital Expenditures Incurred but Not yet Paid	15,393	70,026
Increase (Decrease) in Asset Retirement Obligations	$ 206	$ 42,126
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Shares Issued	0	1,009,015
Operating Lease, Payments	$ 2,224	$ 2,131
Operating Cash Flow from Financing Leases	20	57
Finance Lease, Principal Payments	445	489
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0	4,217
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 917	$ 471