Related Party Transactions (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Accounts payable to related party		$ 30.5		$ 30.5		$ 16.3
Cost of sales	[1]	1,325.6	$ 932.4	2,707.1	$ 1,934.7
Devon Energy Corporation
Related Party Transaction [Line Items]
Accounts receivable balance		122.1		122.1		102.7
Accounts payable to related party		$ 27.0		$ 27.0		$ 16.3
Devon Energy Corporation | Customer Concentration Risk | Sales Revenue, Net
Related Party Transaction [Line Items]
Concentration risk		11.50%	15.80%	10.60%	15.30%
Cedar Cove Joint Venture
Related Party Transaction [Line Items]
Accounts receivable balance		$ 0.6		$ 0.6
Accounts payable to related party		3.5		3.5
Cost of sales		$ 9.5	$ 4.3	$ 22.5	$ 5.5

[1] Includes related party cost of sales of $46.7 million and $50.9 million for the three months ended June 30, 2018 and 2017, respectively, and $80.8 million and $79.6 million for the six months ended June 30, 2018 and 2017, respectively.