UNAUDITED CONSOLIDATED STATEMENT OF CHANGES IN (DEFICIT) EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Financing Receivable	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Preferred Partner Shell Pipeline Company L P	Common Unitholders	Common Unitholders Cumulative Effect, Period of Adoption, Adjustment	Common Unitholders Shell Pipeline Company L P	Common Unitholders Shell Pipeline Company L P Cumulative Effect, Period of Adoption, Adjustment	General Partner SPLC Shell Pipeline Company L P	General Partner SPLC Shell Pipeline Company L P Cumulative Effect, Period of Adoption, Adjustment
Beginning balance at Dec. 31, 2018	$ (257.0)	$ (9.0)		$ 0.0	$ 25.0		$ 3,459.0	$ (4.0)	$ (198.0)	$ (5.0)	$ (3,543.0)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	137.0				5.0		58.0		47.0		27.0
Other contributions from Parent	7.0										7.0
Distributions to unitholders and general partner	(129.0)						(49.0)		(40.0)		(40.0)
Distributions to noncontrolling interests	(3.0)				(3.0)
Ending balance at Mar. 31, 2019	(254.0)			0.0	27.0		3,464.0		(196.0)		(3,549.0)
Beginning balance at Dec. 31, 2018	(257.0)	$ (9.0)		0.0	25.0		3,459.0	$ (4.0)	(198.0)	$ (5.0)	(3,543.0)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	402.0
Ending balance at Sep. 30, 2019	(757.0)			(6.0)	26.0		3,461.0		(196.0)		(4,042.0)
Beginning balance at Mar. 31, 2019	(254.0)			0.0	27.0		3,464.0		(196.0)		(3,549.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	119.0				4.0		45.0		40.0		30.0
Other contributions from Parent	3.0			(6.0)							9.0
Distributions to unitholders and general partner	(119.0)						(51.0)		(42.0)		(26.0)
Distributions to noncontrolling interests	(6.0)				(6.0)
April 2020 Transaction and June 2019 Acquisition	(510.0)										(510.0)
Ending balance at Jun. 30, 2019	(767.0)			(6.0)	25.0		3,458.0		(198.0)		(4,046.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	146.0				5.0		56.0		49.0		36.0
Other contributions from Parent	(1.0)										(1.0)
Distributions to unitholders and general partner	(131.0)						(53.0)		(47.0)		(31.0)
Distributions to noncontrolling interests	(4.0)				(4.0)
Ending balance at Sep. 30, 2019	(757.0)			(6.0)	26.0		3,461.0		(196.0)		(4,042.0)
Beginning balance at Dec. 31, 2019	(749.0)		$ 0.0	(8.0)	26.0	$ 0.0	3,450.0		(203.0)		(4,014.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	142.0				4.0		44.0		39.0		55.0
Distributions to unitholders and general partner	(162.0)						(57.0)		(50.0)		(55.0)
Distributions to noncontrolling interests	(5.0)				(5.0)
Ending balance at Mar. 31, 2020	(774.0)		0.0	(8.0)	25.0	0.0	3,437.0		(214.0)		(4,014.0)
Beginning balance at Dec. 31, 2019	(749.0)		0.0	(8.0)	26.0	0.0	3,450.0		(203.0)		(4,014.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	423.0
Ending balance at Sep. 30, 2020	(414.0)		(300.0)	(6.0)	23.0	(1,059.0)	3,402.0		(2,474.0)		0.0
Beginning balance at Mar. 31, 2020	(774.0)		0.0	(8.0)	25.0	0.0	3,437.0		(214.0)		(4,014.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	144.0				3.0	12.0	41.0		88.0		0.0
Other contributions from Parent	1.0			0.0					1.0		0.0
Distributions to unitholders and general partner	(163.0)						(57.0)		(51.0)		(55.0)
Distributions to noncontrolling interests	(4.0)				(4.0)
Principal repayments on financing receivables	1.0		1.0
April 2020 Transaction and June 2019 Acquisition	416.0		(302.0)			(1,071.0)			(2,280.0)		4,069.0
Ending balance at Jun. 30, 2020	(379.0)		(301.0)	(8.0)	24.0	(1,059.0)	3,421.0		(2,456.0)		0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	137.0				2.0	12.0	38.0		85.0		0.0
Other Comprehensive Income (Loss), Net of Tax	2.0			2.0
Distributions to unitholders and general partner	(172.0)					(12.0)	(57.0)		(103.0)		0.0
Distributions to noncontrolling interests	(3.0)				(3.0)
Principal repayments on financing receivables	1.0		1.0
Ending balance at Sep. 30, 2020	$ (414.0)		$ (300.0)	$ (6.0)	$ 23.0	$ (1,059.0)	$ 3,402.0		$ (2,474.0)		$ 0.0