Components of Working Capital - Accrued Liabilities Table (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Components Of Working Capital [Abstract]
Accrued interest expense		$ 70,968	$ 40,646
Short-term asset retirement obligations		25,938	2,304
Short-term remediation and reclamation obligations		863	833
Income taxes payable		384	2,495
Contract liabilities		16,403	0
Other		14,640	1,714
Total accrued liabilities	[1]	$ 129,196	$ 47,992

[1] Accrued liabilities includes affiliate amounts of $2.4 million and $0.2 million as of December 31, 2018 and 2017, respectively.