Fair Value Measurements - Schedule of Quantitative Information about Level 3 Fair Value Measurements (Details) $ in Millions	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	$ 205	$ 181
Mortgage servicing assets excluded from OREO	9	8
Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	205	181
Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans	207	104
Level 3 | Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	1	0
Insignificant level 3 assets, net of liabilities	3	4
Level 3 | Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans	207	104
Market comparable pricing | Level 3 | Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential)	$ 9	$ 9
Market comparable pricing | Level 3 | Recurring | Comparability factor | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential), measurement input	0.6267	0.6267
Market comparable pricing | Level 3 | Recurring | Comparability factor | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential), measurement input	0.8960	0.8960
Market comparable pricing | Level 3 | Recurring | Comparability factor | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential), measurement input	0.7084	0.7083
Discounted cash flow | Level 3 | Recurring | Interest rate
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	$ 0	$ 2
Discounted cash flow | Level 3 | Recurring | Interest rate | Probability of default | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets, measurement input	0.0002	0.0002
Discounted cash flow | Level 3 | Recurring | Interest rate | Probability of default | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets, measurement input	1	1
Discounted cash flow | Level 3 | Recurring | Interest rate | Probability of default | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets, measurement input	0.0690	0.0530
Discounted cash flow | Level 3 | Recurring | Interest rate | Loss given default | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets, measurement input	0	0
Discounted cash flow | Level 3 | Recurring | Interest rate | Loss given default | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets, measurement input	1	1
Discounted cash flow | Level 3 | Recurring | Interest rate | Loss given default | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets, measurement input	0.500	0.477
Fair value of collateral | Level 3 | Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans	$ 207	$ 104
Fair value of collateral | Level 3 | Nonrecurring | Credit and liquidity discount | Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans, measurement input	0	0
Fair value of collateral | Level 3 | Nonrecurring | Credit and liquidity discount | Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans, measurement input	0.9000	0.1000
Fair value of collateral | Level 3 | Nonrecurring | Credit and liquidity discount | Weighted Average
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans, measurement input	0.1600	0.0500
Appraised value | Level 3 | Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
OREO and other Level 3 assets	$ 16	$ 21