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						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Apr. 01, 2020
Limited Partners Capital Account [Line Items]
Net income	$ 137	$ 144	$ 142	$ 146	$ 119	$ 137	$ 423	$ 402
Less: Net income attributable to noncontrolling interests	2			5			9	14
Net income attributable to the Partnership	135			141			414	388
Distributions declared				140			484	390
Preferred unitholder’s interest in net income attributable to the Partnership	$ 12			0			24	0
Income (less than) / in excess of distributions				1			(94)	(2)
General Partner SPLC
Limited Partners Capital Account [Line Items]
Net income attributable to the Partnership				36				93
Distributions declared				36			55	93
Income (less than) / in excess of distributions				0			0	0
General Partner SPLC | Economic Interest
Limited Partners Capital Account [Line Items]
Noncontrolling interest		2.00%							2.00%
Preferred Partner
Limited Partners Capital Account [Line Items]
Preferred unitholder’s interest in net income attributable to the Partnership				0			24	0
Limited Partners’ Common Units
Limited Partners Capital Account [Line Items]
Net income attributable to the Partnership				105				295
Distributions declared				104			429	297
Income (less than) / in excess of distributions				$ 1			$ (94)	$ (2)