Loans, Leases, and Allowance for Credit Losses (Summary of Nonaccrual Loans) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	$ 66	$ 91
Amortized cost basis with allowance	182	131
Nonaccrual loans that are current	248	222
Related allowance	39	43
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	20	23
Amortized cost basis with allowance	112	81
Nonaccrual loans that are current	132	104
Related allowance	27	32
Commercial \| Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	7	11
Amortized cost basis with allowance	103	71
Nonaccrual loans that are current	110	82
Related allowance	25	30
Commercial \| Owner-occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	13	12
Amortized cost basis with allowance	7	8
Nonaccrual loans that are current	20	20
Related allowance	1	1
Commercial \| Leasing
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	0	0
Amortized cost basis with allowance	2	2
Nonaccrual loans that are current	2
Related allowance	1	1
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	34	59
Amortized cost basis with allowance	9	2
Nonaccrual loans that are current	43	61
Related allowance	1	1
Commercial real estate \| Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	0	22
Amortized cost basis with allowance	1	0
Nonaccrual loans that are current	1	22
Related allowance	0	0
Commercial real estate \| Term
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	34	37
Amortized cost basis with allowance	8	2
Nonaccrual loans that are current	42	39
Related allowance	1	1
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	12	9
Amortized cost basis with allowance	61	48
Nonaccrual loans that are current	73	57
Related allowance	11	10
Consumer \| Home equity credit line
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	4	1
Amortized cost basis with allowance	23	16
Nonaccrual loans that are current	27	17
Related allowance	4	5
Consumer \| 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	8	8
Amortized cost basis with allowance	36	32
Nonaccrual loans that are current	44	40
Related allowance	6	$ 5
Consumer \| Bankcard and other revolving plans
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	0
Amortized cost basis with allowance	1
Nonaccrual loans that are current	1
Related allowance	1
Consumer \| Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis with no allowance	0
Amortized cost basis with allowance	1
Nonaccrual loans that are current	1
Related allowance	$ 0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph c
-Publisher SEC

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Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

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- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

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