INVESTMENTS - Gross Unrealized Losses and Fair Value by Length of Time in Unrealized Loss Position (Detail) $ in Thousands	Mar. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	464	454
Fair Value
Less Than 12 Months	$ 59,634	$ 26,893
12 Months or More	1,016,193	1,050,289
Total	1,075,827	1,077,182
Unrealized Losses
Less Than 12 Months	484	190
12 Months or More	125,440	118,130
Total	$ 125,924	$ 118,320
U.S. treasuries and government agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	9	10
Fair Value
Less Than 12 Months	$ 0	$ 0
12 Months or More	92,236	96,927
Total	92,236	96,927
Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	4,630	4,751
Total	$ 4,630	$ 4,751
State and municipal
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	123	123
Fair Value
Less Than 12 Months	$ 3,789	$ 4,162
12 Months or More	258,977	262,081
Total	262,766	266,243
Unrealized Losses
Less Than 12 Months	48	84
12 Months or More	46,468	43,208
Total	$ 46,516	$ 43,292
Mortgage-backed and asset-backed
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	332	321
Fair Value
Less Than 12 Months	$ 55,845	$ 22,731
12 Months or More	664,980	691,281
Total	720,825	714,012
Unrealized Losses
Less Than 12 Months	436	106
12 Months or More	74,342	70,171
Total	$ 74,778	$ 70,277