ACCUMULATED OTHER COMPREHENSIVE INCOME/ (LOSS) - Reclassification Adjustments Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and dividends on investment securities	$ 170,098	$ 162,411	$ 501,225	$ 471,908
Recognized actuarial loss	0	75	0	526
Income before income tax expense	21,874	27,636	79,938	129,576
Tax expense (benefit)	(5,665)	(6,890)	(20,550)	(32,832)
Net income	$ 16,209	$ 20,746	59,388	96,744
Unrealized Losses on Debt Securities Transferred from Available-for-Sale to Held-to-Maturity | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and dividends on investment securities			(1,137)	(1,314)
Income before income tax expense			(1,137)	(1,314)
Tax expense (benefit)			277	347
Net income			(860)	(967)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Recognized actuarial loss			0	(526)
Pension settlement expense			0	(8,157)
Defined Benefit Pension Plan | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense			0	(8,683)
Tax expense (benefit)			0	2,212
Net income			$ 0	$ (6,471)