Investment Securities - Investment Securities by Credit Rating Type (Detail) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	$ 1,625	$ 1,584
Fair value	18,701	18,788
Investment securities - equity	79	79
AAA
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	1,902	1,760
Investment securities - equity	0	0
AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	16,021	16,090
Investment securities - equity	28	27
A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	436	593
Investment securities - equity	0	0
BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	163	166
Investment securities - equity	21	21
BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	94	92
Investment securities - equity	30	30
Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	1,625	1,584
Fair value	85	87
Investment securities - equity	0	1
Tax-exempt
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	1,463	1,419
Fair value	788	802
Tax-exempt \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	8	8
Tax-exempt \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	355	362
Tax-exempt \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	356	361
Tax-exempt \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	0	0
Tax-exempt \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	0	0
Tax-exempt \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	1,463	1,419
Fair value	69	71
Private label residential MBS
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	162	165
Fair value	1,005	1,039
Private label residential MBS \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	979	1,012
Private label residential MBS \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	26	26
Private label residential MBS \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	0	0
Private label residential MBS \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	0	0
Private label residential MBS \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	0	0
Fair value	0	1
Private label residential MBS \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Amortized cost	162	165
Fair value	0	0
Residential MBS issued by GSEs and GNMA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	7,497	7,230
Residential MBS issued by GSEs and GNMA \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Residential MBS issued by GSEs and GNMA \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	7,497	7,230
Residential MBS issued by GSEs and GNMA \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Residential MBS issued by GSEs and GNMA \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Residential MBS issued by GSEs and GNMA \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Residential MBS issued by GSEs and GNMA \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
U.S. Treasury securities
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	5,610	5,970
U.S. Treasury securities \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
U.S. Treasury securities \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	5,610	5,970
U.S. Treasury securities \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
U.S. Treasury securities \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
U.S. Treasury securities \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
U.S. Treasury securities \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
CLO
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	2,966	2,747
CLO \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	914	739
CLO \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	2,052	1,857
CLO \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	151
CLO \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
CLO \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
CLO \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Commercial MBS issued by GSEs and GNMA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	471	635
Commercial MBS issued by GSEs and GNMA \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	1	1
Commercial MBS issued by GSEs and GNMA \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	470	634
Commercial MBS issued by GSEs and GNMA \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Commercial MBS issued by GSEs and GNMA \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Commercial MBS issued by GSEs and GNMA \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Commercial MBS issued by GSEs and GNMA \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Corporate debt securities
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	297	297
Corporate debt securities \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Corporate debt securities \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Corporate debt securities \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	78	78
Corporate debt securities \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	135	138
Corporate debt securities \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	84	81
Corporate debt securities \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Other
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	67	68
Other \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	0	0
Other \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	11	11
Other \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	2	3
Other \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	28	28
Other \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	10	10
Other \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	16	16
Preferred Stock
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	51	52
Preferred Stock \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
Preferred Stock \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
Preferred Stock \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
Preferred Stock \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	21	21
Preferred Stock \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	30	30
Preferred Stock \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	1
CRA investments
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	28	27
CRA investments \| AAA
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
CRA investments \| AA+ to AA-
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	28	27
CRA investments \| A+ to A-
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
CRA investments \| BBB+ to BBB-
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
CRA investments \| BB+ and below
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	0	0
CRA investments \| Unrated
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	$ 0	$ 0

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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