Shareholders' Equity - Shares Repurchased and Reissued (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 26, 2022	Aug. 31, 2020	Feb. 28, 2019	Apr. 30, 2017
Share repurchases
Repurchase of common shares	$ 2,222	$ 1,647	$ 2,039
Stock repurchase program, authorized amount					$ 2,500	$ 2,500	$ 2,500
Remaining balance under stock repurchase program	$ 432
Shares surrendered upon vesting for income tax obligation	0.3	0.3	0.3
Income tax obligations paid on vesting date	$ 69	$ 52	$ 34
Number of shares reacquired through net settlement of options	1.3	1.5	0.7
Aggregate value of shares reacquired through net settlement of options	$ 306	$ 263	$ 106
Treasury shares reissued for restricted stock award grants, performance share units and issuance of shares vested under advisor deferred compensation plans	0.4	0.5	0.7
Subsequent event
Share repurchases
Stock repurchase program, authorized amount				$ 3,000
Share repurchase authorization
Share repurchases
Repurchase of common shares (in shares)	7.1	8.4	13.4
Repurchase of common shares	$ 1,800	$ 1,300	$ 1,900