Fair Value Measurements - Schedule of Quantitative Information about Level 3 Fair Value Measurements (Details) $ in Millions	Mar. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	$ 368	$ 175
Mortgage servicing assets excluded from OREO	2
Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	368	175
Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans	116	56
Level 3 \| Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	(1)	(2)
Insignificant level 3 assets, net of liabilities	2	4
Level 3 \| Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans	116	56
Market comparable pricing \| Level 3 \| Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential)	$ 11	$ 11
Market comparable pricing \| Level 3 \| Recurring \| Comparability factor \| Minimum
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential), measurement input	0.7130	0.7430
Market comparable pricing \| Level 3 \| Recurring \| Comparability factor \| Maximum
Fair Value, Option, Quantitative Disclosures [Line Items]
Loans, net of unearned income (residential), measurement input	0.9500	0.9900
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	0.8458	0.8499
Discounted cash flow \| Level 3 \| Recurring \| Interest rate
Fair Value, Option, Quantitative Disclosures [Line Items]
Derivative assets	$ (2)	$ (3)
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	0.0480	0.0440
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	0.449	0.485
Fair value of collateral \| Level 3 \| Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Collateral-dependent loans	$ 116	$ 56
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	0.7200	1.0000
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	0.2200	0.4000
Appraised value \| Level 3 \| Nonrecurring
Fair Value, Option, Quantitative Disclosures [Line Items]
OREO and other Level 3 assets	$ 10	$ 8

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