Related Party Transactions - Additional Information (Details)					3 Months Ended	12 Months Ended
		Sep. 15, 2017	Mar. 29, 2016	Nov. 03, 2014 USD ($)	Sep. 30, 2017	Dec. 31, 2017 USD ($) credit_facility	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Statute of limitations expirations, number of days						60 days
Number of days within combined tax filing submission						15 days
Other contributions from Parent	[1]					$ 17,100,000	$ 9,700,000	$ 42,600,000
Gain (loss) from sale of excess allowance oil						1,300,000	1,300,000	(100,000)
Maximum
Related Party Transaction [Line Items]
Indemnification subject to an aggregate limit				$ 15,000,000		$ 10,700,000
364 Day Revolver
Related Party Transaction [Line Items]
Debt instrument term						364 days
Pension and Retirement Savings Plans
Related Party Transaction [Line Items]
Pension and postretirement health and life insurance						$ 4,300,000	5,100,000	5,400,000
Defined benefit plan costs						1,700,000	2,000,000	2,300,000
Management Agreement
Related Party Transaction [Line Items]
General and administrative expense						8,100,000	7,700,000	7,400,000
Omnibus Agreement
Related Party Transaction [Line Items]
General and administrative expense						$ 8,500,000	8,500,000	8,500,000
Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Number of revolving credit facilities | credit_facility						4
Shell Treasury Center West Inc | Five Year Revolver
Related Party Transaction [Line Items]
Debt instrument term		5 years			5 years	5 years
Shell Treasury Center West Inc | 364 Day Revolver
Related Party Transaction [Line Items]
Debt instrument term			364 days			364 days
SPLC
Related Party Transaction [Line Items]
General insurance expense						$ 8,000,000	5,900,000	7,500,000
Operations and maintenance costs allocated from parent						17,100,000	15,900,000	17,100,000
General and administrative costs allocated from parent						26,300,000	24,000,000	22,400,000
SPLC | Reimbursement for Maintenance Expense and Capital Expenditures
Related Party Transaction [Line Items]
Other contributions from Parent						0	1,600,000
Zydeco Mars Bengal Poseidon Explorer and Colonial
Related Party Transaction [Line Items]
Total distributions to general partners						235,700,000	186,200,000	133,500,000
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Reimbursements related to costs and expenses for maintenance projects						$ 16,100,000	$ 3,000,000	$ 12,900,000
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Payment of general and administrative fee				$ 8,500,000
Zydeco Pipeline Company LLC (“Zydeco”)
Related Party Transaction [Line Items]
Noncontrolling interest						7.50%	7.50%	37.50%
Odyssey Pipeline L.L.C.
Related Party Transaction [Line Items]
Noncontrolling interest						29.00%	29.00%	29.00%
Mars | Shell Pipeline Company L P
Related Party Transaction [Line Items]
Reimbursements related to costs and expenses for maintenance projects								$ 2,900,000
Shell Oil Products US (SOPUS) | Shell Pipeline Company L P
Related Party Transaction [Line Items]
Reimbursements related to costs and expenses for maintenance projects								4,500,000
Lockport | Shell Pipeline Company L P
Related Party Transaction [Line Items]
Reimbursements related to costs and expenses for maintenance projects						$ 1,700,000	$ 1,600,000	1,800,000
Zydeco Pipeline Company LLC (“Zydeco”) | Shell Pipeline Company L P
Related Party Transaction [Line Items]
Reimbursements related to costs and expenses for maintenance projects						$ 14,400,000	$ 1,400,000	$ 2,300,000

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