Shareholders' Equity - Shares Repurchased and Reissued (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jul. 24, 2023	Jan. 31, 2022
Share repurchases
Repurchase of common shares	$ 2,212	$ 2,095	$ 2,222
Stock repurchase program, authorized amount				$ 3,500	$ 3,000
Remaining balance under stock repurchase program	$ 3,100
Shares surrendered upon vesting for income tax obligation (in shares)	0.3	0.3	0.3
Income tax obligations paid on vesting date	$ 99	$ 99	$ 69
Shares reacquired through net settlement of options (in shares)	0.4	0.5	1.3
Aggregate value of shares reacquired through net settlement of options	$ 150	$ 145	$ 306
Treasury shares reissued for restricted stock award grants, performance share units and issuance of shares vested under advisor deferred compensation plans (in shares)	0.6	0.8	0.4
Share repurchase authorization
Share repurchases
Repurchase of common shares (in shares)	5.9	6.6	7.1
Repurchase of common shares	$ 2,000	$ 1,900	$ 1,800