Investments - Investment Securities Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	$ 90,958	$ 175,099
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	1,580	7,984
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	132,242	60,615
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	9,599	4,637
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	223,200	235,714
Available-for Sale, Gross Unrealized Losses, Total	11,179	12,621
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	66,649	100,190
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	1,276	5,748
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	70,620	27,446
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	6,881	2,682
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	137,269	127,636
Available-for Sale, Gross Unrealized Losses, Total	8,157	8,430
Corporate Bonds [Member]
Marketable Securities [Line Items]
Available-for Sale, Fair value of Investments with Unrealized Losses, Less Than 12 Months	24,309	71,069
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	304	1,790
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	43,472	19,000
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	1,576	993
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	67,781	90,069
Available-for Sale, Gross Unrealized Losses, Total	1,880	2,783
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	3,840
Available-for Sale, Gross Unrealized Losses, Less Than 12 Months	0	446
Available-for Sale, Fair Value of Investments with Unrealized Losses, 12 Months or Greater	4,003	219
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	403	40
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	4,003	4,059
Available-for Sale, Gross Unrealized Losses, Total	403	486
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	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	14,147	13,950
Available-for Sale, Gross Unrealized Losses, 12 Months or Greater	739	922
Available-for Sale, Fair Value of Investments with Unrealized Losses, Total	14,147	13,950
Available-for Sale, Gross Unrealized Losses, Total	$ 739	$ 922

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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