INVESTMENTS - Gross Unrealized Losses and Fair Value by Length of Time of Available-For-Sale Securities (Detail) $ in Thousands	Jun. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	70	34
Fair Value
Less Than 12 Months	$ 429,113	$ 92,868
12 Months or More	7,383	76,879
Total	436,496	169,747
Unrealized Losses
Less Than 12 Months	8,543	367
12 Months or More	38	693
Total	$ 8,581	$ 1,060
U.S. treasuries and government agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	1	2
Fair Value
Less Than 12 Months	$ 4,968	$ 25,369
12 Months or More	0	0
Total	4,968	25,369
Unrealized Losses
Less Than 12 Months	8	2
12 Months or More	0	0
Total	$ 8	$ 2
State and municipal
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	27	8
Fair Value
Less Than 12 Months	$ 74,184	$ 22,753
12 Months or More	0	0
Total	74,184	22,753
Unrealized Losses
Less Than 12 Months	1,872	211
12 Months or More	0	0
Total	$ 1,872	$ 211
Mortgage-backed and asset-backed
Debt Securities, Available-for-sale [Line Items]
Number of Securities | security	42	24
Fair Value
Less Than 12 Months	$ 349,961	$ 44,746
12 Months or More	7,383	76,879
Total	357,344	121,625
Unrealized Losses
Less Than 12 Months	6,663	154
12 Months or More	38	693
Total	$ 6,701	$ 847