Parent Company Financial Statements - Condensed Statement of Cash Flow - Parent Company Only (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net Income	$ 2,770	$ 1,427	$ 2,512
Adjustments to reconcile net income to net cash provided by operating activities:
(Benefit from) provision for deferred income taxes	(14)	(162)	(246)
Equity in undistributed earnings	(30)	(12)	(12)
Net change in:
Equity securities	15	12	(29)
Other assets	(37)	(855)	20
Net Cash Provided by Operating Activities	2,704	371	1,824
Investing Activities
Other short-term investments and federal funds sold	(1,172)	(31,446)	(612)
Net Cash Used in Investing Activities	(7,968)	(31,902)	(797)
Financing Activities
Dividends paid on common and preferred stock	(897)	(858)	(753)
Proceeds from issuance of long-term debt	562	2,557	3,866
Repayment of long-term debt	(3,603)	(2,799)	(4,212)
Issuance of preferred stock	0	346	242
Repurchase of treasury stock and related forward contract	(1,393)	0	(1,763)
Other, net	(99)	(47)	(58)
Net Cash Provided by (Used in) Financing Activities	5,111	31,400	(430)
Cash and Due from Banks at Beginning of Period	3,147	3,278	2,681
Cash and Due from Banks at End of Period	2,994	3,147	3,278
Parent Company
Operating Activities
Net Income	2,770	1,427	2,512
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization and accretion	7	7	7
(Benefit from) provision for deferred income taxes	(1)	0	(11)
Securities gains, net	(1)	(1)	(2)
Equity in undistributed earnings	64	(351)	(594)
Net change in:
Equity securities	1	0	(49)
Other assets	(40)	(1)	(80)
Accrued expenses and other liabilities	(80)	0	127
Net Cash Provided by Operating Activities	2,720	1,081	1,910
Investing Activities
Other short-term investments and federal funds sold	(656)	(855)	(1,081)
Loans to nonbank subsidiaries	158	94	127
Net cash paid on acquisition	0	0	(469)
Net Cash Used in Investing Activities	(498)	(761)	(1,423)
Financing Activities
Net change in other short-term borrowings	(89)	91	106
Dividends paid on common and preferred stock	(897)	(858)	(753)
Proceeds from issuance of long-term debt	498	1,243	2,235
Repayment of long-term debt	(250)	(1,100)	(500)
Issuance of preferred stock	0	346	242
Repurchase of treasury stock and related forward contract	(1,393)	0	(1,763)
Other, net	(89)	(40)	(56)
Net Cash Provided by (Used in) Financing Activities	(2,220)	(318)	(489)
Increase (Decrease) in Cash	2	2	(2)
Cash and Due from Banks at Beginning of Period	120	118	120
Cash and Due from Banks at End of Period	$ 122	$ 120	$ 118