Earnings per Unit - Basic and Diluted Earnings 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
Allocation of net income among partner interests:
Net income attributable to common unitholders	$ 223	$ 351	$ 610	$ 854
Class A common units
Allocation of net income among partner interests:
Net income attributable to common unitholders	$ 145	$ 201	$ 395	$ 478
Denominator - basic and diluted partnership units:
Total weighted average basic and diluted units outstanding (in shares)	202	202	202	202
Earnings per unit - basic and diluted:
Earnings per unit - basic and diluted (in usd per share)	$ 0.72	$ 1.00	$ 1.96	$ 2.37
Partnership exchangeable units
Allocation of net income among partner interests:
Net income attributable to common unitholders	$ 78	$ 150	$ 215	$ 376
Denominator - basic and diluted partnership units:
Total weighted average basic and diluted units outstanding (in shares)	162	197	164	204
Earnings per unit - basic and diluted:
Earnings per unit - basic and diluted (in usd per share)	$ 0.48	$ 0.76	$ 1.31	$ 1.85