Loans and ACL - Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2022		Jun. 30, 2021	Jun. 30, 2022		Jun. 30, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses	$ 171		$ (434)	$ 76		$ (386)
Commercial: | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,319		2,136	1,426		2,204
Charge-Offs	(17)		(53)	(48)		(132)
Recoveries	13		23	30		42
Provision for credit losses	42		(302)	(51)		(310)
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	1,357		1,804	1,357		1,804
Commercial: | CRE
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	283		544	350		573
Charge-Offs	(1)		0	(2)		(4)
Recoveries	6		4	7		5
Provision for credit losses	(51)		(108)	(118)		(134)
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	237		440	237		440
Commercial: | Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	53		77	52		81
Charge-Offs	0		0	(1)		(2)
Recoveries	1		1	2		2
Provision for credit losses	(4)		(9)	(3)		(12)
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	50		69	50		69
Consumer: | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	310		343	308		368
Charge-Offs	(2)		(4)	(4)		(15)
Recoveries	4		5	10		7
Provision for credit losses	15		(23)	13		(39)
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	327		321	327		321
Consumer: | Residential home equity and direct
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	574		707	615		714
Charge-Offs	(85)		(57)	(143)		(112)
Recoveries	20		20	40		38
Provision for credit losses	79		24	76		54
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	588		694	588		694
Consumer: | Indirect auto
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	957		1,176	1,022		1,198
Charge-Offs	(77)		(69)	(179)		(174)
Recoveries	26		27	49		49
Provision for credit losses	46		(18)	60		43
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	952		1,116	952		1,116
Consumer: | Indirect other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	211		187	195		208
Charge-Offs	(18)		(11)	(37)		(28)
Recoveries	6		7	12		13
Provision for credit losses	29		(2)	58		(12)
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	228		181	228		181
Consumer: | Student
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	115		131	117		130
Charge-Offs	(4)		(3)	(10)		(6)
Recoveries	0		0	0		0
Provision for credit losses	(10)		0	(7)		2
Allowance for Loan and Lease Losses, Adjustments, Other	(1)	[1]	1	0	[1]	3	[1]
Ending balance	100		129	100		129
Credit card
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	348		361	350		359
Charge-Offs	(40)		(42)	(81)		(82)
Recoveries	9		10	18		19
Provision for credit losses	31		38	61		71
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	348		367	348		367
ALLL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4,170		5,662	4,435		5,835
Charge-Offs	(244)		(239)	(505)		(555)
Recoveries	85		97	168		175
Provision for credit losses	177		(400)	89		(337)
Allowance for Loan and Lease Losses, Adjustments, Other	(1)	[1]	1	0	[1]	3	[1]
Ending balance	4,187		5,121	4,187		5,121
RUFC
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	253		349	260		364
Charge-Offs	0		0	0		0
Recoveries	0		0	0		0
Provision for credit losses	(6)		(34)	(13)		(49)
Allowance for Loan and Lease Losses, Adjustments, Other	0	[1]	0	0	[1]	0	[1]
Ending balance	247		315	247		315
ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4,423		6,011	4,695		6,199
Charge-Offs	(244)		(239)	(505)		(555)
Recoveries	85		97	168		175
Provision for credit losses	171		(434)	76		(386)
Allowance for Loan and Lease Losses, Adjustments, Other	(1)	[1]	1	0	[1]	3	[1]
Ending balance	$ 4,434		$ 5,436	$ 4,434		$ 5,436

[1] Includes the amounts for the ALLL for PCD acquisitions, and other activity.