Net Income Per Limited Partner Unit - Schedule of Allocation of Net Income to Arrive at Net Income Per Limited Partner Unit (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Limited Partners Capital Account [Line Items]
Net income		$ 556	$ 546	$ 482
Net income attributable to noncontrolling interests		13	18	18
Net income attributable to the Partnership		543	528	464
Partner distribution declared		645	552	469
Preferred unitholder’s interest in net income	$ 36	36	0	0
Income (less than)/in excess of distributions		(138)	(24)	(5)
General Partner SPLC
Limited Partners Capital Account [Line Items]
Net income attributable to the Partnership			147	134
Partner distribution declared		55	148	135
Income (less than)/in excess of distributions		$ 0	(1)	(1)
General Partner SPLC | Economic Interest
Limited Partners Capital Account [Line Items]
Noncontrolling interest	2.00%	2.00%
Limited Partners Common Units
Limited Partners Capital Account [Line Items]
Net income attributable to the Partnership			381	330
Partner distribution declared		$ 590	404	334
Income (less than)/in excess of distributions		(138)	(23)	(4)
Preferred Partner
Limited Partners Capital Account [Line Items]
Preferred unitholder’s interest in net income		$ 36	$ 0	$ 0