Parent Company Financial Information - Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Dividend income:
Other income (loss)	$ 103	$ 75	$ 67
Interest on term borrowings	72	72	72
Personnel expense	1,100	1,101	1,210
Income before income taxes	1,128	1,159	1,284
Income tax benefit	212	247	274
Equity in undistributed net income (loss) of subsidiaries:
Net income attributable to controlling interest	897	900	999
Parent Company
Dividend income:
Bank	220	435	770
Non-bank	0	16	0
Total dividend income	220	451	770
Other income (loss)	226	22	(26)
Total income	446	473	744
Interest on term borrowings	21	31	31
Personnel expense	114	128	89
Total expense	135	159	120
Income before income taxes	311	314	624
Income tax benefit	24	(31)	(35)
Income before equity in undistributed net income of subsidiaries	287	345	659
Equity in undistributed net income (loss) of subsidiaries:
Bank	613	561	332
Non-bank	(3)	(6)	8
Net income attributable to controlling interest	$ 897	$ 900	$ 999