ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Accumulated Other Comprehensive (loss) income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Accumulated other comprehensive (loss) income, net of tax:
Balance	$ 1,191,253	$ 1,169,583	$ 1,155,287	$ 1,192,620	$ 1,169,583	$ 1,192,620
Other comprehensive loss, net of tax	(5,747)	(4,259)	(20,570)	(43,199)	(10,006)	(63,769)
Balance	1,202,503	1,191,253	1,140,522	1,155,287	1,202,503	1,140,522
Accumulated Other Comprehensive Loss, Net of Deferred Taxes
Accumulated other comprehensive (loss) income, net of tax:
Balance	(98,638)	(94,379)	(49,380)	(6,181)	(94,379)	(6,181)
Other comprehensive (loss) income before reclassifications					(11,586)	(63,156)
Amounts reclassified from accumulated other comprehensive loss					1,580	(613)
Other comprehensive loss, net of tax	(5,747)	(4,259)	(20,570)	(43,199)	(10,006)	(63,769)
Balance	(104,385)	(98,638)	(69,950)	(49,380)	(104,385)	(69,950)
Securities
Accumulated other comprehensive (loss) income, net of tax:
Balance		(100,870)		(7,864)	(100,870)	(7,864)
Other comprehensive (loss) income before reclassifications					(12,259)	(70,803)
Amounts reclassified from accumulated other comprehensive loss					2,111	685
Other comprehensive loss, net of tax					(10,148)	(70,118)
Balance	(111,018)		(77,982)		(111,018)	(77,982)
Defined Benefit Plans
Accumulated other comprehensive (loss) income, net of tax:
Balance		(5,266)		(1,306)	(5,266)	(1,306)
Other comprehensive (loss) income before reclassifications					729	1,368
Amounts reclassified from accumulated other comprehensive loss					(521)	(1,282)
Other comprehensive loss, net of tax					208	86
Balance	(5,058)		(1,220)		(5,058)	(1,220)
Derivatives
Accumulated other comprehensive (loss) income, net of tax:
Balance		$ 11,757		$ 2,989	11,757	2,989
Other comprehensive (loss) income before reclassifications					(56)	6,279
Amounts reclassified from accumulated other comprehensive loss					(10)	(16)
Other comprehensive loss, net of tax					(66)	6,263
Balance	$ 11,691		$ 9,252		$ 11,691	$ 9,252