PARENT COMPANY FINANCIALS - Condensed Statements of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING INCOME:
Total interest income	$ 4,851	$ 5,357	$ 6,189
OPERATING EXPENSE:
Salaries and employee benefits	2,132	2,123	2,026
Interest expense	339	771	1,575
All other expenses	411	419	476
Income before income tax expense	2,977	1,298	2,251
Income taxes	658	241	460
NET INCOME	2,319	1,057	1,791
Other comprehensive income (loss), net of income taxes:
Total other comprehensive income (loss), net of income taxes	(605)	351	680
Total comprehensive income (loss)	1,714	1,408	2,471
Parent company
OPERATING INCOME:
Dividends from banking subsidiaries	1,120	900	1,130
Interest	35	42	48
Management and service fees	64	54	42
All other operating income	1	1	1
Total interest income	1,279	1,041	1,233
OPERATING EXPENSE:
Salaries and employee benefits	36	27	35
Interest expense	119	120	87
All other expenses	28	30	27
Total operating expense	183	177	149
Income before income tax expense	1,096	864	1,084
Income taxes	(16)	(16)	(10)
Income before undistributed income of subsidiaries and associated companies	1,112	880	1,094
NET INCOME	2,319	1,057	1,791
Other comprehensive income (loss), net of income taxes:
Net pension plan activity arising during the period	4	(3)	(5)
Net unrealized derivative instrument gains (losses) arising during the period	1	2	2
Net other comprehensive loss	5	(1)	(3)
Other comprehensive income (loss) activity of Bank subsidiaries, net of income taxes	(610)	352	683
Total other comprehensive income (loss), net of income taxes	(605)	351	680
Total comprehensive income (loss)	1,714	1,408	2,471
Nonbank subsidiaries | Parent company
OPERATING INCOME:
Interest	2	4	4
Dividends from nonbank subsidiaries	57	40	8
OPERATING EXPENSE:
Equity in undistributed income (losses) of subsidiaries and associated companies	19	7	15
Bank subsidiaries | Parent company
OPERATING EXPENSE:
Equity in undistributed income (losses) of subsidiaries and associated companies	$ 1,188	$ 170	$ 682