CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) BY COMPONENT (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 1,863,558	$ 1,746,865	$ 1,836,683	$ 1,638,394
Unrealized gains (losses) arising during period, before tax	25,215	32,810	3,955	36,439
Income tax effect	(6,671)	(8,432)	(1,068)	(9,351)
Other comprehensive income (loss) before reclassifications	18,544	24,378	2,887	27,088
Reclassification adjustments for (gains) losses included in net income, before tax	1,226	0	54,342	749
Income tax effect	(324)	0	(14,296)	(193)
Amounts reclassified from accumulated other comprehensive income (loss) to net income	902	0	40,046	556
Amortization of unrealized loss on securities transferred from available-for-sale to held-to-maturity	1,074	1,209	3,449	3,821
Income tax effect	(284)	(311)	(911)	(978)
Amortization of unrealized loss on securities transferred from available for sale to held to maturity	790	898	2,538	2,843
Other comprehensive income (loss), net of income tax effect	20,236	25,276	45,471	30,487
Ending balance	2,126,059	1,801,180	2,126,059	1,801,180
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(71,325)	(131,358)	(96,560)	(136,569)
Other comprehensive income (loss), net of income tax effect	20,236	25,276	45,471	30,487
Ending balance	(51,089)	(106,082)	(51,089)	(106,082)
Unrealized Gains (Losses) on Available for Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(71,325)	(131,358)	(96,560)	(136,569)
Unrealized gains (losses) arising during period, before tax	22,929	32,810	1,669	36,439
Income tax effect	(6,066)	(8,432)	(463)	(9,351)
Other comprehensive income (loss) before reclassifications	16,863	24,378	1,206	27,088
Reclassification adjustments for (gains) losses included in net income, before tax	(186)	0	52,930	749
Income tax effect	49	0	(13,923)	(193)
Amounts reclassified from accumulated other comprehensive income (loss) to net income	(137)	0	39,007	556
Amortization of unrealized loss on securities transferred from available-for-sale to held-to-maturity	1,074	1,209	3,449	3,821
Income tax effect	(284)	(311)	(911)	(978)
Amortization of unrealized loss on securities transferred from available for sale to held to maturity	790	898	2,538	2,843
Other comprehensive income (loss), net of income tax effect	17,516	25,276	42,751	30,487
Ending balance	(53,809)	(106,082)	(53,809)	(106,082)
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	0	0	0	0
Unrealized gains (losses) arising during period, before tax	2,286	0	2,286	0
Income tax effect	(605)	0	(605)	0
Other comprehensive income (loss) before reclassifications	1,681	0	1,681	0
Reclassification adjustments for (gains) losses included in net income, before tax	1,412	0	1,412	0
Income tax effect	(373)	0	(373)	0
Amounts reclassified from accumulated other comprehensive income (loss) to net income	1,039	0	1,039	0
Amortization of unrealized loss on securities transferred from available-for-sale to held-to-maturity	0	0	0	0
Income tax effect	0	0	0	0
Amortization of unrealized loss on securities transferred from available for sale to held to maturity	0	0	0	0
Other comprehensive income (loss), net of income tax effect	2,720	0	2,720	0
Ending balance	$ 2,720	$ 0	$ 2,720	$ 0