Net Income Per Limited Partner Unit (Schedule of Earnings Per unit of our Limited Partners) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Limited Partners' Capital Account [Line Items]
Net income attributable to the Partnership	$ 206	$ 237	$ 687	$ 668
Less:
Distributions declared	210	206	628	576
Distributions less than (more than) net income attributable to the Partnership	(4)	31	59	92
General Partner
Limited Partners' Capital Account [Line Items]
Net income attributable to the Partnership				140
Less:
Distributions declared	0	0	0	139
Preferred Units | Limited Partner
Limited Partners' Capital Account [Line Items]
Net income attributable to the Partnership	10	9	29	28
Less:
Distributions declared	10	9	29	28
Common Units | Limited Partner
Limited Partners' Capital Account [Line Items]
Net income attributable to the Partnership	196	228	658	500
Less:
Distributions declared	$ 200	$ 197	$ 599	$ 409