Revenue from Contracts with Customers - Contract Liabilities Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Change in Contracts with Customer, Liability [Roll Forward]
Balance at December 31, 2018	$ 145,624
Cash received or receivable, excluding revenues recognized during the period	75,166
Revenues recognized that were included in the contract liability balance at the beginning of the period	(12,110)
Cumulative catch-up adjustment for change in estimated consideration due to an annual cost-of-service rate update	13,594
Balance at December 31, 2019	222,274
Contract liabilities at December 31, 2019
Accrued liabilities		$ 19,659	$ 16,235
Other liabilities		202,615
Total contract liabilities from contracts with customers	$ 222,274	$ 222,274	$ 145,624