Related Party Transactions - Schedule of Other Related Party Balances (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Accounts receivable	$ 16.2	$ 12.1	[1]
Prepaid expenses	0.6	3.2
Other assets	0.7	0.0
Accounts payable	10.5	5.4	[1]
Deferred revenue	20.8	7.9	[1]
Accrued liabilities	5.9	5.1	[1]
Debt payable	1,000.6	686.0	[1]
Lease liability	0.0	24.9
Accrued interest, related parties	5.5	2.6
Other accrued liabilities, related parties	0.4	0.9
Fuel accrual, related parties		1.6
Unamortized debt issuance costs	1.3	0.9
Affiliated Entity
Related Party Transaction [Line Items]
Unamortized debt issuance costs	$ 1.3	$ 0.9

[1] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.