Loans and ACL - Allowance for Credit Losses (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses		$ 502	$ (95)
Commercial: | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		1,409	1,426
Charge-Offs		(75)	(31)
Recoveries		13	17
Provision for credit losses		151	(93)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	(1)	0
Ending balance		1,497	1,319
Commercial: | CRE
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		224	350
Charge-Offs		(6)	(1)
Recoveries		1	1
Provision for credit losses		32	(67)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	0	0
Ending balance		251	283
Commercial: | Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		46	52
Charge-Offs		0	(1)
Recoveries		1	1
Provision for credit losses		40	1
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	0	0
Ending balance		87	53
Consumer: | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		399	308
Charge-Offs		(1)	(2)
Recoveries		2	6
Provision for credit losses		13	(2)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	(81)	0
Ending balance		332	310
Consumer: | Home equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		90	96
Charge-Offs		(2)	(1)
Recoveries		6	5
Provision for credit losses		(7)	(12)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	0	0
Ending balance		87	88
Consumer: | Indirect auto
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		981	1,022
Charge-Offs		(127)	(102)
Recoveries		26	23
Provision for credit losses		100	14
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	13	0
Ending balance		993	957
Consumer: | Other consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		770	714
Charge-Offs		(105)	(76)
Recoveries		17	21
Provision for credit losses		98	38
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	(1)	0
Ending balance		779	697
Consumer: | Student
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		98	117
Charge-Offs		(5)	(6)
Recoveries		0	0
Provision for credit losses		5	3
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	0	1
Ending balance		98	115
Credit card
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		360	350
Charge-Offs		(51)	(41)
Recoveries		9	9
Provision for credit losses		40	30
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	(3)	0
Ending balance		355	348
ALLL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		4,377	4,435
Charge-Offs		(372)	(261)
Recoveries		75	83
Provision for credit losses		472	(88)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	(73)	1
Ending balance		4,479	4,170
RUFC
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		272	260
Charge-Offs		0	0
Recoveries		0	0
Provision for credit losses		10	(7)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	0	0
Ending balance		282	253
ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		4,649	4,695
Charge-Offs		(372)	(261)
Recoveries		75	83
Provision for credit losses		482	(95)
Allowance for Loan and Lease Losses, Adjustments, Other	[1]	(73)	1
Ending balance		$ 4,761	$ 4,423

[1] Includes the amounts for the ALLL for PCD acquisitions, the impact of adopting the Troubled Debt Restructurings and Vintage Disclosures accounting standard, and other activity.