INVESTMENTS - Estimated Fair Values and Amortized Costs of Debt Securities Available-for-sale by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value
Total available-for-sale debt securities	$ 1,465,896	$ 1,348,021
Amortized Cost
Total available-for-sale debt securities	1,466,350	1,310,159
U.S. treasuries and government agencies
Fair Value
One year or less	12,029	33,963
One to five years	56,510	9,334
Five to ten years	0	0
After ten years	0	0
Amortized Cost
One year or less	11,995	33,833
One to five years	56,492	8,917
Five to ten years	0	0
After ten years	0	0
State and municipal
Fair Value
One year or less	12,821	16,581
One to five years	27,408	44,910
Five to ten years	42,960	59,059
After ten years	243,213	269,817
Amortized Cost
One year or less	12,709	16,458
One to five years	26,637	43,857
Five to ten years	42,661	56,130
After ten years	241,279	260,663
Mortgage-backed and asset-backed
Fair Value
One year or less	9,272	1
One to five years	14,752	21,637
Five to ten years	388,918	74,142
After ten years	658,013	808,652
Amortized Cost
One year or less	9,239	1
One to five years	14,575	21,229
Five to ten years	390,569	72,481
After ten years	660,194	787,490
Corporate debt
Fair Value
One year or less	0	0
One to five years	0	2,318
Five to ten years	0	7,607
After ten years	0	0
Amortized Cost
One year or less	0	0
One to five years	0	2,100
Five to ten years	0	7,000
After ten years	$ 0	$ 0