Investment Securities - Summary of Maturities of Securities Available for Sale by Amortized Cost and Estimated Fair Value (Detail) - USD ($) $ in Thousands |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Investments, Debt and Equity Securities [Abstract] | ||
| Due in one year or less, Amortized Cost | $ 292,924 | $ 298,573 |
| Due after one year through five years, Amortized Cost | 518,718 | 527,383 |
| Due after five years through ten years, Amortized Cost | 514,207 | 559,647 |
| Due after ten years, Amortized Cost | 2,496,396 | 1,879,257 |
| Amortized Cost | 3,822,245 | 3,264,860 |
| Due in one year or less, Estimated Fair Value | 292,540 | 298,193 |
| Due after one year through five years, Estimated Fair Value | 478,794 | 494,204 |
| Due after five years through ten years, Estimated Fair Value | 464,232 | 521,011 |
| Due after ten years, Estimated Fair Value | 2,264,929 | 1,746,044 |
| Total available for sale securities | $ 3,500,495 | $ 3,059,452 |
| X | ||||||||||
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount, after allowance for credit loss, of 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). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amortized cost, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- References No definition available.
|