v3.26.1
Investment Securities - Investment Securities by Credit Rating Type (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost $ 1,676 $ 1,584
Fair value 18,880 18,788
Investment securities - equity 80 79
AAA    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 2,127 1,760
Investment securities - equity 0 0
AA+ to AA-    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 16,046 16,090
Investment securities - equity 28 27
A+ to A-    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 389 593
Investment securities - equity 0 0
BBB+ to BBB-    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 151 166
Investment securities - equity 21 21
BB+ and below    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 18 92
Investment securities - equity 30 30
Unrated    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 1,676 1,584
Fair value 149 87
Investment securities - equity 1 1
Tax-exempt    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 1,517 1,419
Fair value 794 802
Tax-exempt | AAA    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 55 8
Tax-exempt | AA+ to AA-    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 349 362
Tax-exempt | A+ to A-    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 328 361
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 1,517 1,419
Fair value 62 71
Private label residential MBS    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 159 165
Fair value 1,136 1,039
Private label residential MBS | AAA    
Schedule of Held-to-Maturity Securities [Line Items]    
Amortized cost 0 0
Fair value 1,110 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 159 165
Fair value 0 0
Residential MBS issued by GSEs and GNMA    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 7,428 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 7,428 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 5,494 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 5,494 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 3,221 2,747
CLO | AAA    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 961 739
CLO | AA+ to AA-    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 2,208 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 52 0
Commercial MBS issued by GSEs and GNMA    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 514 635
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 513 634
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 222 297
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 19 0
Corporate debt securities | A+ to A-    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 59 78
Corporate debt securities | BBB+ to BBB-    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 122 138
Corporate debt securities | BB+ and below    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 8 81
Corporate debt securities | Unrated    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 14 0
Other    
Schedule of Held-to-Maturity Securities [Line Items]    
Fair value 71 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 9 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 29 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 21 16
Preferred Stock    
Schedule of Held-to-Maturity Securities [Line Items]    
Investment securities - equity 52 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 1 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