Net Income Per Limited Partner Unit - Schedule of Basic and Diluted Net Income Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Distribution Made To Limited Partner [Line Items]
Distributions declared		$ 140	$ 484	$ 390
Income (less than) / in excess of distributions		1	(94)	(2)
Net income attributable to the Partnership	$ 135	141	414	388
Net income attributable to the Partnership's common unitholders (basic)			390
General Partner SPLC
Distribution Made To Limited Partner [Line Items]
Distributions declared		36	55	93
Income (less than) / in excess of distributions		0	0	0
Net income attributable to the Partnership		36		93
Net income attributable to the Partnership's common unitholders (basic)			55
Limited Partners’ Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared		104	429	297
Income (less than) / in excess of distributions		1	(94)	(2)
Net income attributable to the Partnership		$ 105		$ 295
Net income attributable to the Partnership's common unitholders (basic)			335
Dilutive effect of preferred units			24
Net income attributable to the Partnership's common unitholders (diluted)	$ 135		$ 359
Weighted average units outstanding (in millions)
Weighted average units outstanding - Basic (in shares)	393.3		340.1
Dilutive effect of preferred units (in shares)	50.8		33.9
Weighted average units outstanding - Diluted (in shares)	444.1		374.0
Weighted average units outstanding, basic and diluted (in shares)		233.3		227.9
Net income per Limited Partner Unit (in dollars)
Net income per Limited Partner Unit - basic (in dollars per share)	$ 0.31	$ 0.45	$ 0.98	$ 1.30
Net income per Limited Partner Unit - diluted (in dollars per share)	$ 0.30	0.45	$ 0.96	1.30
Net income per Limited Partner unit, basic and diluted (in dollars per share)		$ 0.45		$ 1.30