Components of Working Capital - Accrued Liabilities Table (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Components Of Working Capital [Abstract]
Accrued interest expense		$ 45,624	$ 39,834
Short-term asset retirement obligations		3,976	3,114
Short-term remediation and reclamation obligations		630	630
Income taxes payable		1,024	1,006
Other accrued liabilities		6,445	606
Total accrued liabilities	[1]	$ 57,699	$ 45,190

[1] Accrued liabilities includes affiliate amounts of $0.3 million and zero as of September 30, 2017, and December 31, 2016, respectively.