Derivative Instruments and Hedging Activities - Schedule of Effect of Hedging Derivative Instruments in the Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Derivative [Line Items]
Loans, including fees	$ 1,260	$ 548
Investment securities	197	87
Deposits	521	274
FHLB advances and other borrowings	59	29
Loans, including fees \| Fair Value Hedges
Derivative [Line Items]
Recognized on derivatives	0	0
Recognized on hedged items	0	0
Pre-tax income (loss) recognized on cash flow hedges	0	0
Investment securities \| Fair Value Hedges
Derivative [Line Items]
Recognized on derivatives	(6)	(17)
Recognized on hedged items	6	17
Pre-tax income (loss) recognized on cash flow hedges	0	0
Deposits \| Fair Value Hedges
Derivative [Line Items]
Recognized on derivatives	(5)	0
Recognized on hedged items	5	0
Pre-tax income (loss) recognized on cash flow hedges	0	0
FHLB advances and other borrowings \| Fair Value Hedges
Derivative [Line Items]
Recognized on derivatives	(13)	12
Recognized on hedged items	13	(12)
Pre-tax income (loss) recognized on cash flow hedges	$ 0	$ 0

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
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-Publisher FASB
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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.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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Amount of unrealized gain (loss) included in earnings related to the fair value of the hedged item in an interest rate fair value hedge, offset by the gain (loss) on the hedging instrument to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Interest and fee income generated by loans the Entity intends and has the ability to hold for the foreseeable future, or until maturity or payoff, including commercial and consumer loans, whether domestic or foreign, which may consist of: (1) industrial and agricultural; (2) real estate; and (3) real estate construction loans; (4) trade financing; (5) lease financing; (6) home equity lines-of-credit; (7) automobile and other vehicle loans; and (8) credit card and other revolving-type loans. Also includes interest income for leases held by the Entity.

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Aggregate amount of interest expense on all deposits.

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Interest expense incurred during the reporting period on short-term borrowings associated with Federal Home Loan Bank and Federal Reserve Bank advances.

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Amount of interest income, amortization of premium and accretion of discount, on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading); classified as operating.

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