PARENT COMPANY FINANCIALS - Condensed Cash Flow Statements (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net income		$ 2,319	$ 1,057	$ 1,791
Deferred income taxes		(429)	(238)	64
Increase (decrease) in other liabilities		757	1,001	331
(Increase) decrease in other assets		(1,719)	(3,979)	(853)
Net change due to operating activities		2,275	111	1,697
INVESTING ACTIVITIES
Acquisitions, net of cash acquired		(165)	(3)	(129)
Other		(316)	(65)	(106)
Net change due to investing activities		(10,486)	(6,136)	(3,875)
FINANCING ACTIVITIES
Proceeds from issuance of long-term borrowed funds		0	8,323	12,850
Repayments of long-term borrowed funds		(1,352)	(14,022)	(14,857)
Treasury stock purchased		(295)	(270)	(1,220)
Net proceeds from issuance of preferred stock		296	395	730
Redemption of preferred stock		(250)	0	0
Dividends declared and paid to preferred stockholders		(113)	(98)	(65)
Net change due to financing activities		4,636	15,372	1,490
Net change in cash and cash equivalents		(3,575)	9,347	(688)
Cash and cash equivalents at beginning of period	[1]	12,733	3,386	4,074
Cash and cash equivalents at end of period	[1]	9,158	12,733	3,386
Parent company
OPERATING ACTIVITIES
Net income		2,319	1,057	1,791
Deferred income taxes		0	17	(8)
Equity in undistributed earnings of subsidiaries		(1,207)	(177)	(697)
Increase (decrease) in other liabilities		34	43	50
(Increase) decrease in other assets		12	(41)	7
Other operating, net		67	48	58
Net change due to operating activities		1,225	947	1,201
INVESTING ACTIVITIES
Investments in and advances to subsidiaries		(196)	(190)	(105)
Repayment of investments in and advances to subsidiaries		125	205	55
Acquisitions, net of cash acquired		(165)	0	0
Other		(1)	(1)	(1)
Net change due to investing activities		(237)	14	(51)
FINANCING ACTIVITIES
Proceeds from issuance of long-term borrowed funds		0	1,053	500
Repayments of long-term borrowed funds		(350)	(12)	0
Treasury stock purchased		(295)	(270)	(1,220)
Net proceeds from issuance of preferred stock		296	395	730
Redemption of preferred stock		(250)	0	0
Dividends declared and paid to common stockholders		(670)	(672)	(617)
Dividends declared and paid to preferred stockholders		(113)	(98)	(65)
Other financing, net		(20)	(95)	(21)
Net change due to financing activities		(1,402)	301	(693)
Net change in cash and cash equivalents		(414)	1,262	457
Cash and cash equivalents at beginning of period		2,680	1,418	961
Cash and cash equivalents at end of period		$ 2,266	$ 2,680	$ 1,418

[1] Cash and cash equivalents include cash and due from banks and interest-bearing cash and due from banks as reflected on the Consolidated Balance Sheets