CAPITAL RATIOS AND SHAREHOLDERS' EQUITY - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning accumulated other comprehensive income	$ 5,882	$ 2,868	$ 6,740	$ 3,792	$ 6,740	$ 3,792
Total other comprehensive (loss) income	(2,994)	1,263	(858)	(924)	(3,852)	339
Ending accumulated other comprehensive income	2,888	4,131	5,882	2,868	2,888	4,131
Net unrealized gain (loss) on AFS securities
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning accumulated other comprehensive income	7,237	11,412	10,023	5,550	10,023	5,550
Other comprehensive gain (loss) before reclassifications	(1,367)	269			(4,114)	7,265
Less: amounts reclassified from accumulated other comprehensive income	1,472	0			1,511	1,134
Total other comprehensive (loss) income	(2,839)	269			(5,625)	6,131
Ending accumulated other comprehensive income	4,398	11,681	7,237	11,412	4,398	11,681
Net unrealized gain (loss) on hedging derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning accumulated other comprehensive income	63	(7,387)	(1,865)	(601)	(1,865)	(601)
Other comprehensive gain (loss) before reclassifications	(155)	994			1,773	(5,792)
Less: amounts reclassified from accumulated other comprehensive income	0	0			0	0
Total other comprehensive (loss) income	(155)	994			1,773	(5,792)
Ending accumulated other comprehensive income	(92)	(6,393)	63	(7,387)	(92)	(6,393)
Net unrealized gain (loss) on post-retirement plans
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning accumulated other comprehensive income	(1,418)	(1,157)	(1,418)	(1,157)	(1,418)	(1,157)
Other comprehensive gain (loss) before reclassifications	0	0			0	0
Less: amounts reclassified from accumulated other comprehensive income	0	0			0	0
Total other comprehensive (loss) income	0	0			0	0
Ending accumulated other comprehensive income	(1,418)	(1,157)	(1,418)	(1,157)	(1,418)	(1,157)
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax
Beginning accumulated other comprehensive income	5,882	2,868	6,740	3,792	6,740	3,792
Other comprehensive gain (loss) before reclassifications	(1,522)	1,263			(2,341)	1,473
Less: amounts reclassified from accumulated other comprehensive income	1,472	0			1,511	1,134
Total other comprehensive (loss) income	(2,994)	1,263	(858)	(924)	(3,852)	339
Ending accumulated other comprehensive income	$ 2,888	$ 4,131	$ 5,882	$ 2,868	$ 2,888	$ 4,131