Loans, Leases, and Allowance for Credit Losses (Summary of Selected Information on TDRs) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	$ 316	$ 326
Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	34	36
Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	58	51
Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	8	8
Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	58	50
Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	69	73
Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	89	108
Accruing
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	216	221
Accruing | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	24	30
Accruing | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	54	46
Accruing | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	7	7
Accruing | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	36	35
Accruing | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	60	60
Accruing | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	35	43
Accruing | Commercial
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	84	84
Accruing | Commercial | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	20	24
Accruing | Commercial | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	24	15
Accruing | Commercial | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	9	8
Accruing | Commercial | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	18	18
Accruing | Commercial | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	13	19
Accruing | Commercial | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	37	31
Accruing | Commercial | Commercial and industrial | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	19	19
Accruing | Commercial | Commercial and industrial | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	10	1
Accruing | Commercial | Commercial and industrial | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Commercial and industrial | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Commercial and industrial | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	4	4
Accruing | Commercial | Commercial and industrial | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	4	7
Accruing | Commercial | Owner-occupied
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	37	43
Accruing | Commercial | Owner-occupied | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	5
Accruing | Commercial | Owner-occupied | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	4	4
Accruing | Commercial | Owner-occupied | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Owner-occupied | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	9	8
Accruing | Commercial | Owner-occupied | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	14	14
Accruing | Commercial | Owner-occupied | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	9	12
Accruing | Commercial | Municipal
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	10	10
Accruing | Commercial | Municipal | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Municipal | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	10	10
Accruing | Commercial | Municipal | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Municipal | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Municipal | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial | Municipal | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial real estate
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	106	106
Accruing | Commercial real estate | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Accruing | Commercial real estate | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	29	29
Accruing | Commercial real estate | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial real estate | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	27	27
Accruing | Commercial real estate | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	41	41
Accruing | Commercial real estate | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	8	8
Accruing | Commercial real estate | Term
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	106	106
Accruing | Commercial real estate | Term | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Accruing | Commercial real estate | Term | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	29	29
Accruing | Commercial real estate | Term | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Commercial real estate | Term | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	27	27
Accruing | Commercial real estate | Term | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	41	41
Accruing | Commercial real estate | Term | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	8	8
Accruing | Consumer
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	26	31
Accruing | Consumer | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	5
Accruing | Consumer | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	2
Accruing | Consumer | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	7	7
Accruing | Consumer | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Consumer | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Accruing | Consumer | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	14	16
Accruing | Consumer | Home equity credit line
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	7	8
Accruing | Consumer | Home equity credit line | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Consumer | Home equity credit line | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	1
Accruing | Consumer | Home equity credit line | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	5	5
Accruing | Consumer | Home equity credit line | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Consumer | Home equity credit line | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Consumer | Home equity credit line | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	2	2
Accruing | Consumer | 1-4 family residential
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	19	23
Accruing | Consumer | 1-4 family residential | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	5
Accruing | Consumer | 1-4 family residential | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Accruing | Consumer | 1-4 family residential | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	2	2
Accruing | Consumer | 1-4 family residential | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Accruing | Consumer | 1-4 family residential | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Accruing | Consumer | 1-4 family residential | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	12	14
Nonaccruing
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	100	105
Nonaccruing | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	10	6
Nonaccruing | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	4	5
Nonaccruing | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	22	15
Nonaccruing | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	9	13
Nonaccruing | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	54	65
Nonaccruing | Commercial
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	79	84
Nonaccruing | Commercial | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	10	6
Nonaccruing | Commercial | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	4
Nonaccruing | Commercial | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	11	4
Nonaccruing | Commercial | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	7	8
Nonaccruing | Commercial | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	48	62
Nonaccruing | Commercial | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	58	64
Nonaccruing | Commercial | Commercial and industrial | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Commercial | Commercial and industrial | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	4
Nonaccruing | Commercial | Commercial and industrial | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial | Commercial and industrial | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	11	2
Nonaccruing | Commercial | Commercial and industrial | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	7	8
Nonaccruing | Commercial | Commercial and industrial | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	36	49
Nonaccruing | Commercial | Owner-occupied
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	21	20
Nonaccruing | Commercial | Owner-occupied | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	9	5
Nonaccruing | Commercial | Owner-occupied | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial | Owner-occupied | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial | Owner-occupied | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	2
Nonaccruing | Commercial | Owner-occupied | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial | Owner-occupied | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	12	13
Nonaccruing | Commercial real estate
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	16	16
Nonaccruing | Commercial real estate | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial real estate | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial real estate | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial real estate | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	11	11
Nonaccruing | Commercial real estate | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	2	2
Nonaccruing | Commercial real estate | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	3
Nonaccruing | Commercial real estate | Term
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	16	16
Nonaccruing | Commercial real estate | Term | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial real estate | Term | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial real estate | Term | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Commercial real estate | Term | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	11	11
Nonaccruing | Commercial real estate | Term | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	2	2
Nonaccruing | Commercial real estate | Term | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	3
Nonaccruing | Consumer
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	5	5
Nonaccruing | Consumer | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Consumer | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Consumer | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	3
Nonaccruing | Consumer | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	3	0
Nonaccruing | Consumer | Home equity credit line
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Consumer | Home equity credit line | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | Home equity credit line | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | Home equity credit line | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Consumer | Home equity credit line | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | Home equity credit line | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | Home equity credit line | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | 1-4 family residential
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	4	4
Nonaccruing | Consumer | 1-4 family residential | Interest rate below market
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | 1-4 family residential | Maturity or term extension
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	1	1
Nonaccruing | Consumer | 1-4 family residential | Principal forgiveness
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | 1-4 family residential | Payment deferral
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	0
Nonaccruing | Consumer | 1-4 family residential | Other
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	0	3
Nonaccruing | Consumer | 1-4 family residential | Multiple modification types
Financing Receivable, Modifications [Line Items]
Amortized cost resulting from the following modification types	$ 3	$ 0