INVESTMENTS - Gross Unrealized Losses and Fair Value by Length of Time in Unrealized Loss Position (Detail) $ in Thousands	Sep. 30, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	454	454
Fair Value
Less Than 12 Months	$ 96,111	$ 26,893
12 Months or More	942,569	1,050,289
Total	1,038,680	1,077,182
Unrealized Losses
Less Than 12 Months	568	190
12 Months or More	91,777	118,130
Total	$ 92,345	$ 118,320
U.S. treasuries and government agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	8	10
Fair Value
Less Than 12 Months	$ 0	$ 0
12 Months or More	84,807	96,927
Total	84,807	96,927
Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	2,430	4,751
Total	$ 2,430	$ 4,751
State and municipal
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	118	123
Fair Value
Less Than 12 Months	$ 1,781	$ 4,162
12 Months or More	250,438	262,081
Total	252,219	266,243
Unrealized Losses
Less Than 12 Months	167	84
12 Months or More	38,489	43,208
Total	$ 38,656	$ 43,292
Mortgage-backed and asset-backed
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	328	321
Fair Value
Less Than 12 Months	$ 94,330	$ 22,731
12 Months or More	607,324	691,281
Total	701,654	714,012
Unrealized Losses
Less Than 12 Months	401	106
12 Months or More	50,858	70,171
Total	$ 51,259	$ 70,277