Share-Based Payments - Summary of TSRU and PTU Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Total Shareholder Return Units (TSRUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units outstanding, shares	230,539,000	[1],[2]
Units vested, shares	100,696,000	[1],[2]
Units expected to vest, shares	124,594,000	[1],[2],[3]
Units outstanding, weighted average grant price (in dollars per share) | $ / shares	$ 29.57	[1],[2]
Units vested, weighted average grant price (in dollars per share) | $ / shares	25.22	[1],[2]
Units expected to vest, weighted average grant price (in dollars per share) | $ / shares	$ 32.94	[1],[2],[3]
Units outstanding, weighted average remaining contractual term	2 years 3 months 18 days	[1],[2]
Units vested, weighted average remaining contractual term	9 months 18 days	[1],[2]
Units expected to vest, weighted average remaining contractual term	3 years 3 months 18 days	[1],[2],[3]
Units outstanding, aggregate intrinsic value | $	$ 1,737	[1],[2]
Units vested, aggregate intrinsic value | $	1,168	[1],[2]
Units expected to vest, aggregate intrinsic value | $	$ 547	[1],[2],[3]
Units settled, shares	5,478,547
Units settled, weighted average grant price (in dollars per share) | $ / shares	$ 30.93
Units exercised, shares	2,217,044
Units exercised, weighted average grant price (in dollars per share) | $ / shares	$ 29.26
Profit Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units outstanding, shares	1,467,000	[1],[2]
Units outstanding, weighted average remaining contractual term	3 months 18 days	[1],[2]
Units outstanding, aggregate intrinsic value | $	$ 54	[1],[2]
Units granted upon conversion, shares	757,285

[1] In 2020, 2,217,044 TSRUs with a weighted-average grant price of $29.26 per unit were converted into 757,285 PTUs.

[2] In 2020, we settled 5,478,547 TSRUs with a weighted-average grant price of $30.93 per unit.

[3] The number of TSRUs expected to vest takes into account an estimate of expected forfeitures.