Related Party Transactions (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Accounts payable to related party		$ 16.0		$ 16.3
Cost of sales	[1]	1,381.5	$ 1,002.3
Devon Energy Corporation
Related Party Transaction [Line Items]
Accounts receivable balance		115.1		102.7
Accounts payable to related party		$ 16.0		$ 16.3
Devon Energy Corporation | Customer Concentration Risk | Sales Revenue, Net
Related Party Transaction [Line Items]
Concentration risk		9.80%	14.90%
Cedar Cove Joint Venture
Related Party Transaction [Line Items]
Cost of sales		$ 13.0	$ 1.2

[1] Includes related party cost of sales of $34.1 million and $28.7 million for the three months ended March 31, 2018 and 2017, respectively.