Investment securities - Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($)
$ in Thousands |
Jun. 30, 2026 |
Dec. 31, 2025 |
| Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
| AFS, less than 12 months, fair value |
$ 13,143,000
|
$ 662,000
|
| AFS, less than 12 months, gross unrealized losses |
150,000
|
3,000
|
| AFS, 12 months or longer, fair value |
1,093,000
|
1,554,000
|
| AFS, 12 months or longer, gross unrealized losses |
62,000
|
59,000
|
| Fair Value |
14,236,000
|
2,216,000
|
| Unrealized Losses |
212,000
|
62,000
|
| Total investment securities, less than 12 months, fair value |
15,154,000
|
844,000
|
| Total investment securities, less than 12 months, gross unrealized losses |
180,000
|
4,000
|
| Total investment securities, 12 months or longer, fair value |
9,479,000
|
11,938,000
|
| Total investment securities, 12 months or longer, gross unrealized losses |
833,000
|
795,000
|
| Fair Value |
24,633,000
|
12,782,000
|
| Unrealized Losses |
1,013,000
|
799,000
|
| Schedule of Held-to-Maturity Securities [Line Items] |
|
|
| HTM, less than 12 months, fair value |
2,011,000
|
182,000
|
| HTM, Less than 12 months, gross unrealized losses |
30,000
|
1,000
|
| HTM, 12 months or longer, fair value |
8,386,000
|
10,384,000
|
| HTM, 12 months or longer, gross unrealized losses |
771,000
|
736,000
|
| Fair Value |
10,397,000
|
10,566,000
|
| Unrealized Losses |
801,000
|
737,000
|
| U.S. Treasury |
|
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
| AFS, less than 12 months, fair value |
1,388,000
|
0
|
| AFS, less than 12 months, gross unrealized losses |
4,000
|
0
|
| AFS, 12 months or longer, fair value |
0
|
185,000
|
| AFS, 12 months or longer, gross unrealized losses |
0
|
2,000
|
| Fair Value |
1,388,000
|
185,000
|
| Unrealized Losses |
4,000
|
2,000
|
| Schedule of Held-to-Maturity Securities [Line Items] |
|
|
| HTM, less than 12 months, fair value |
0
|
0
|
| HTM, Less than 12 months, gross unrealized losses |
0
|
0
|
| HTM, 12 months or longer, fair value |
395,000
|
391,000
|
| HTM, 12 months or longer, gross unrealized losses |
3,000
|
4,000
|
| Fair Value |
395,000
|
391,000
|
| Unrealized Losses |
3,000
|
4,000
|
| Commercial |
|
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
| AFS, less than 12 months, fair value |
1,961,000
|
174,000
|
| AFS, less than 12 months, gross unrealized losses |
11,000
|
1,000
|
| AFS, 12 months or longer, fair value |
1,000
|
65,000
|
| AFS, 12 months or longer, gross unrealized losses |
0
|
0
|
| Fair Value |
1,962,000
|
239,000
|
| Unrealized Losses |
11,000
|
1,000
|
| Schedule of Held-to-Maturity Securities [Line Items] |
|
|
| HTM, less than 12 months, fair value |
272,000
|
28,000
|
| HTM, Less than 12 months, gross unrealized losses |
6,000
|
0
|
| HTM, 12 months or longer, fair value |
1,632,000
|
1,840,000
|
| HTM, 12 months or longer, gross unrealized losses |
86,000
|
74,000
|
| Fair Value |
1,904,000
|
1,868,000
|
| Unrealized Losses |
92,000
|
74,000
|
| Residential (b) |
|
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
| AFS, less than 12 months, fair value |
9,794,000
|
488,000
|
| AFS, less than 12 months, gross unrealized losses |
135,000
|
2,000
|
| AFS, 12 months or longer, fair value |
1,091,000
|
1,303,000
|
| AFS, 12 months or longer, gross unrealized losses |
62,000
|
57,000
|
| Fair Value |
10,885,000
|
1,791,000
|
| Unrealized Losses |
197,000
|
59,000
|
| Schedule of Held-to-Maturity Securities [Line Items] |
|
|
| HTM, less than 12 months, fair value |
1,231,000
|
139,000
|
| HTM, Less than 12 months, gross unrealized losses |
19,000
|
1,000
|
| HTM, 12 months or longer, fair value |
5,110,000
|
6,287,000
|
| HTM, 12 months or longer, gross unrealized losses |
644,000
|
618,000
|
| Fair Value |
6,341,000
|
6,426,000
|
| Unrealized Losses |
663,000
|
619,000
|
| Other |
|
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
| AFS, less than 12 months, fair value |
0
|
0
|
| AFS, less than 12 months, gross unrealized losses |
0
|
0
|
| AFS, 12 months or longer, fair value |
1,000
|
1,000
|
| AFS, 12 months or longer, gross unrealized losses |
0
|
0
|
| Fair Value |
1,000
|
1,000
|
| Unrealized Losses |
0
|
0
|
| State and political subdivisions |
|
|
| Schedule of Held-to-Maturity Securities [Line Items] |
|
|
| HTM, less than 12 months, fair value |
508,000
|
13,000
|
| HTM, Less than 12 months, gross unrealized losses |
5,000
|
0
|
| HTM, 12 months or longer, fair value |
1,248,000
|
1,866,000
|
| HTM, 12 months or longer, gross unrealized losses |
38,000
|
40,000
|
| Fair Value |
1,756,000
|
1,879,000
|
| Unrealized Losses |
43,000
|
40,000
|
| Privately issued |
|
|
| Schedule of Held-to-Maturity Securities [Line Items] |
|
|
| HTM, less than 12 months, fair value |
0
|
2,000
|
| HTM, Less than 12 months, gross unrealized losses |
0
|
0
|
| HTM, 12 months or longer, fair value |
1,000
|
0
|
| HTM, 12 months or longer, gross unrealized losses |
0
|
0
|
| Fair Value |
1,000
|
2,000
|
| Unrealized Losses |
$ 0
|
$ 0
|