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	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Distribution Made To Limited Partner [Line Items]
Distributions declared	$ 645	$ 552	$ 469
Income (less than)/in excess of distributions	(138)	(24)	(5)
Net income attributable to the Partnership	543	528	464
Net income attributable to the Partnership’s common unitholders (basic)	507
General Partner SPLC
Distribution Made To Limited Partner [Line Items]
Distributions declared	55	148	135
Income (less than)/in excess of distributions	0	(1)	(1)
Net income attributable to the Partnership		147	134
Net income attributable to the Partnership’s common unitholders (basic)	55
Limited Partners Common Units
Distribution Made To Limited Partner [Line Items]
Distributions declared	590	404	334
Income (less than)/in excess of distributions	(138)	(23)	(4)
Net income attributable to the Partnership		$ 381	$ 330
Net income attributable to the Partnership’s common unitholders (basic)	452
Dilutive effect of preferred units	36
Net income attributable to the Partnership’s common unitholders (diluted)	$ 488
Weighted average units outstanding:
Weighted average units outstanding - Basic (in shares)	353.5
Dilutive effect of preferred units (in shares)	38.2	229.2	220.3
Weighted average units outstanding - Diluted (in shares)	391.7
Net income per limited partner unit:
Basic and diluted (in dollars per share)	$ 1.28	$ 1.66	$ 1.50
Common - Diluted (in dollars per share)	$ 1.25	$ 1.66	$ 1.50