(Deficit) Equity - At-the-Market Program (Details) - USD ($)			3 Months Ended		12 Months Ended
	Feb. 06, 2018	Sep. 15, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Issuance of common units, maximum (in units)					$ 300,000,000
Consideration for units issued in connection with private placement					$ 0	$ 20,000,000	$ 6,000,000
Five Year Revolver due July 2023
Class of Stock [Line Items]
Debt instrument term					5 years
Five Year Revolver due July 2023 | Revolving Credit Facility
Class of Stock [Line Items]
Debt instrument term					5 years
Common units - SPLC
Class of Stock [Line Items]
Units issued in connection with private placement (in units)	11,029,412		5,200,000	94,925	1,000,000,000
Net proceeds from private equity placement	$ 300,000,000		$ 140,000,000	$ 3,000,000
Common units per share (in units per share)	$ 27.20		$ 26.96	$ 31.51
Consideration for units issued in connection with private placement	$ 6,000,000
General Partner
Class of Stock [Line Items]
Units issued in connection with private placement (in units)	225,091		106,122	1,938
Consideration for units issued in connection with private placement			$ 3,000,000
General Partner | General Partner Interest
Class of Stock [Line Items]
Aggregate percentage of interest					2.00%
Shell Pipeline Company L P | General Partner | General Partner Interest
Class of Stock [Line Items]
Aggregate percentage of interest	2.00%	2.00%			2.00%