Parent Company Financial Statements - Condensed Statement of Cash Flow - Parent Company Only (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating Activities
Net Income	$ 2,314	$ 2,349	$ 2,446
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion	495	462	436
Provision for (benefit from) deferred income taxes	72	(106)	(60)
Equity in undistributed earnings	(18)	(52)	(22)
Net change in:
Equity securities	(3)	(128)	70
Other assets	(625)	326	646
Net Cash Provided by Operating Activities	2,824	4,509	6,428
Investing Activities
Proceeds from repayments / maturities of AFS and HTM securities and other investments	5,814	4,235	4,495
Other short-term investments	4,962	(13,731)	26,224
Net Cash Provided by (Used in) Investing Activities	1,039	(9,488)	(4,871)
Financing Activities
Proceeds from long-term debt issuances/advances	3,249	4,286	4,026
Repayment of long-term debt	(5,282)	(1,657)	(1,762)
Dividends paid on common and preferred stock	(1,176)	(1,060)	(927)
Repurchase of treasury stock and related forward contract	(625)	(200)	(100)
Other, net	(65)	(55)	(85)
Net Cash (Used in) Provided by Financing Activities	(3,991)	4,655	(1,085)
(Decrease) Increase in Cash and Due from Banks	(128)	(324)	472
Parent Company
Operating Activities
Net Income	2,314	2,349	2,446
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion	7	7	7
Provision for (benefit from) deferred income taxes	2	1	(3)
Securities (gains) losses, net	(3)	(4)	9
Equity in undistributed earnings	(891)	(915)	(2,533)
Net change in:
Equity securities	8	4	6
Other assets	(49)	147	(115)
Accrued expenses and other liabilities	(60)	(126)	45
Net Cash Provided by Operating Activities	1,328	1,463	(138)
Investing Activities
Proceeds from repayments / maturities of AFS and HTM securities and other investments	1,000	1,000	0
Purchase of securities issued by subsidiary	(2,500)	(1,000)	(1,000)
Other short-term investments	3,394	(833)	567
Loans to nonbank subsidiaries	(5)	60	132
Net Cash Provided by (Used in) Investing Activities	1,889	(773)	(301)
Financing Activities
Net change in other short-term borrowings	3	(121)	(240)
Proceeds from long-term debt issuances/advances	1,742	1,244	2,986
Repayment of long-term debt	(2,250)	(500)	(1,200)
Dividends paid on common and preferred stock	(1,176)	(1,060)	(927)
Repurchase of treasury stock and related forward contract	(625)	(200)	(100)
Other, net	(62)	(53)	(82)
Net Cash (Used in) Provided by Financing Activities	(2,368)	(690)	437
(Decrease) Increase in Cash and Due from Banks	849	0	(2)
Cash and Due from Banks at Beginning of Period	120	120	122
Cash and Due from Banks at End of Period	$ 969	$ 120	$ 120