Investments - Investment Securities Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	$ 72,352	$ 34,429
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	656	642
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	88,654	123,699
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	6,325	6,297
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	161,006	158,128
Available-for Sale, Gross Unrealized Losses, Total	6,981	6,939
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	31,270	28,892
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	346	634
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	61,717	76,440
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	4,896	4,848
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	92,987	105,332
Available-for Sale, Gross Unrealized Losses, Total	5,242	5,482
Corporate Bonds [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	37,261	5,537
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	292	8
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	19,093	31,115
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	657	717
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	56,354	36,652
Available-for Sale, Gross Unrealized Losses, Total	949	725
U.S. Agency-Based Mortgage-Backed Securities [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	0	0
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	0	0
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	3,329	3,641
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	339	305
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	3,329	3,641
Available-for Sale, Gross Unrealized Losses, Total	339	305
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	3,821	0
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	18	0
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	4,515	12,503
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	433	427
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	8,336	12,503
Available-for Sale, Gross Unrealized Losses, Total	$ 451	$ 427

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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