UNAUDITED CONSOLIDATED STATEMENT OF CHANGES IN (DEFICIT) EQUITY - USD ($) $ in Millions	Total	Noncontrolling Interests	Accumulated Other Comprehensive Loss	Common Unitholders	Common Unitholders Shell Pipeline Company L P	General Partner Shell Pipeline Company L P
Beginning balance at Dec. 31, 2017	$ (566.0)	$ 23.0		$ 2,774.0	$ (507.0)	$ (2,856.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	65.0	1.0		21.0	16.0	27.0
Net proceeds from equity offerings	973.0			673.0	300.0
Contributions from general partner	20.0					20.0
Other contributions from Parent	5.0					5.0
Distributions to unitholders and general partner	(83.0)			(33.0)	(30.0)	(20.0)
Distributions to noncontrolling interests	(2.0)	(2.0)
Ending balance at Mar. 31, 2018	410.0	22.0		3,434.0	(220.0)	(2,826.0)
Beginning balance at Dec. 31, 2017	(566.0)	23.0		2,774.0	(507.0)	(2,856.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	335.0
Ending balance at Sep. 30, 2018	(282.0)	23.0		3,451.0	(205.0)	(3,551.0)
Beginning balance at Mar. 31, 2018	410.0	22.0		3,434.0	(220.0)	(2,826.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	115.0	4.0		43.0	36.0	32.0
Other contributions from Parent	2.0					2.0
Distributions to unitholders and general partner	(106.0)			(43.0)	(35.0)	(28.0)
Acquisition	(738.0)					(738.0)
Distributions to noncontrolling interests	(4.0)	(4.0)
Ending balance at Jun. 30, 2018	(321.0)	22.0		3,434.0	(219.0)	(3,558.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	155.0	6.0		62.0	50.0	37.0
Other contributions from Parent	2.0					2.0
Distributions to unitholders and general partner	(113.0)			(45.0)	(36.0)	(32.0)
Distributions to noncontrolling interests	(5.0)	(5.0)
Ending balance at Sep. 30, 2018	(282.0)	23.0		3,451.0	(205.0)	(3,551.0)
Beginning balance at Dec. 31, 2018	(257.0)	25.0	$ 0.0	3,459.0	(198.0)	(3,543.0)
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)	27.0	0.0	3,464.0	(196.0)	(3,549.0)
Beginning balance at Dec. 31, 2018	(257.0)	25.0	0.0	3,459.0	(198.0)	(3,543.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	402.0
Ending balance at Sep. 30, 2019	(757.0)	26.0	(6.0)	3,461.0	(196.0)	(4,042.0)
Beginning balance at Mar. 31, 2019	(254.0)	27.0	0.0	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)
Acquisition	(510.0)					(510.0)
Distributions to noncontrolling interests	(6.0)	(6.0)
Ending balance at Jun. 30, 2019	(767.0)	25.0	(6.0)	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 distributions to 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)	$ 26.0	$ (6.0)	$ 3,461.0	$ (196.0)	$ (4,042.0)