Fair Value Accounting - Change in Level 3 Assets Unobservable Inputs (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Loans held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 700.0	$ 3.0
Purchases and additions	522.0	65.0
Sales and payments	(225.0)	(9.0)
Transfers from Level 2 to Level 3	2.0	2.0
Change in fair value	12.0	2.0
Balance, end of period	1,011.0	63.0
Change in unrealized gains for the period	15.0	1.0
Servicing Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,494.0	1,127.0
Purchases and additions	295.0	260.0
Sales and payments	(211.0)	(83.0)
Change in fair value	22.0	(20.0)
Realization of cash flows	(84.0)	(43.0)
Balance, end of period	1,516.0	1,241.0
Change in unrealized gains for the period	22.0	(19.0)
Interest rate lock commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	19.0	(2.0)
Purchases and additions	5,540.0	5,742.0
Settlement of IRLCs upon acquisition or origination of loans HFS	(5,560.0)	(5,733.0)
Change in fair value	(2.0)	6.0
Balance, end of period	(3.0)	13.0
Change in unrealized gains for the period	(3.0)	13.0
Warrants
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	39.0	30.0
Purchases and additions	2.0	3.0
Warrant exercises	(2.0)
Change in fair value	1.0	(2.0)
Balance, end of period	40.0	31.0
Change in unrealized gains for the period	$ (1.0)	$ (1.0)

Amount of unrealized gain (loss) recognized in income from asset (liability) measured at fair value on recurring basis using unobservable input (level 3) and still held.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Topic 820
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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
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- Definition

IRLC, settlements upon acquisition or origination of loans held for sale

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- Definition

Realization of cash flows

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No definition available.

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