INVESTMENTS - Amortized Cost and Estimated Fair Values of Investments Available-for-sale (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities	$ 1,466,350	$ 1,310,159
Investments available-for-sale:	1,465,896	1,348,021
Available-for-Sale Securities
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities	1,466,350	1,310,159
Gross Unrealized Gains	14,966	38,922
Gross Unrealized Losses	(15,420)	(1,060)
Investments available-for-sale:	1,465,896	1,348,021
Available-for-Sale Securities \| U.S. treasuries and government agencies
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities	68,487	42,750
Gross Unrealized Gains	202	549
Gross Unrealized Losses	(150)	(2)
Investments available-for-sale:	68,539	43,297
Available-for-Sale Securities \| State and municipal
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities	323,286	377,108
Gross Unrealized Gains	6,561	13,470
Gross Unrealized Losses	(3,445)	(211)
Investments available-for-sale:	326,402	390,367
Available-for-Sale Securities \| Mortgage-backed and asset-backed
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities	1,074,577	881,201
Gross Unrealized Gains	8,203	24,078
Gross Unrealized Losses	(11,825)	(847)
Investments available-for-sale:	1,070,955	904,432
Available-for-Sale Securities \| Corporate debt
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale debt securities	0	9,100
Gross Unrealized Gains	0	825
Gross Unrealized Losses	0	0
Investments available-for-sale:	$ 0	$ 9,925

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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