Related Party Transactions - Schedule of Reimbursement from Parent (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Related Party Transaction [Line Items]
Receivable from Parent	$ 0.0	$ 0.2	[1]	$ 1.8	[1]
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Cash received	15.8	2.8		11.1
Receivable from Parent	0.3	0.2		1.8
Total reimbursements	$ 16.1	$ 3.0		$ 12.9

[1] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.