Securities - Summary of Debt Securities with Unrealized Losses, Segregated by Duration of Unrealized Loss (Detail) $ in Thousands	Mar. 31, 2024 USD ($) Investments	Dec. 31, 2023 USD ($) Investments
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	154	155
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 93,367	$ 6,324
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	829	97
Available-for-sale Securities, 12 Months or Longer, Fair Value	1,403,088	1,436,062
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	67,853	66,004
Available-for-sale Securities, Fair Value, Total	1,496,455	1,442,386
Available-for-sale Securities, Unrealized Losses, Total	$ 68,682	$ 66,101
U.S. Treasuries [Member]
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	67	68
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 90,252	$ 4,838
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	816	90
Available-for-sale Securities, 12 Months or Longer, Fair Value	1,370,129	1,401,669
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	64,391	62,545
Available-for-sale Securities, Fair Value, Total	1,460,381	1,406,507
Available-for-sale Securities, Unrealized Losses, Total	$ 65,207	$ 62,635
U.S. Federal Agencies [Member]
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	3	3
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 1,057	$ 1,100
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	4	3
Available-for-sale Securities, Fair Value, Total	1,057	1,100
Available-for-sale Securities, Unrealized Losses, Total	$ 4	$ 3
Mortgage Backed Securities [Member]
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	71	74
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 1,191	$ 80
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	6
Available-for-sale Securities, 12 Months or Longer, Fair Value	12,767	13,261
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	1,789	1,677
Available-for-sale Securities, Fair Value, Total	13,958	13,341
Available-for-sale Securities, Unrealized Losses, Total	$ 1,795	$ 1,677
States and Political Subdivisions [Member]
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	9	6
Available-for-sale Securities, Less than 12 Months, Fair Value	$ 867	$ 306
Available-for-sale Securities, Less than 12 Months, Unrealized Losses	3	4
Available-for-sale Securities, 12 Months or Longer, Fair Value	2,128	1,847
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	134	110
Available-for-sale Securities, Fair Value, Total	2,995	2,153
Available-for-sale Securities, Unrealized Losses, Total	$ 137	$ 114
Asset backed Securities [Member]
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	1	1
Available-for-sale Securities, 12 Months or Longer, Fair Value	$ 11,252	$ 12,512
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	188	282
Available-for-sale Securities, Fair Value, Total	11,252	12,512
Available-for-sale Securities, Unrealized Losses, Total	$ 188	$ 282
Other Securities [Member]
Debt Securities, Available-for-Sale [Abstract]
Number of investments \| Investments	3	3
Available-for-sale Securities, 12 Months or Longer, Fair Value	$ 6,812	$ 6,773
Available-for-sale Securities, 12 Months or Longer, Unrealized Losses	1,351	1,390
Available-for-sale Securities, Fair Value, Total	6,812	6,773
Available-for-sale Securities, Unrealized Losses, Total	$ 1,351	$ 1,390

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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