COMPREHENSIVE INCOME - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Comprehensive Income
Gain (loss) on sale of available-for-sale securities, net									$ 914	$ (166)	$ 327
Salaries and employee benefits									(61,629)	(56,175)	(46,224)
Interest on investment securities									2,448	3,055	3,580
Income from continuing operations, before income taxes									46,943	35,014	15,376
Income tax expense									(9,532)	(8,450)	(3,373)
Net income	$ 11,838	$ 6,491	$ 18,034	$ 1,048	$ 4,095	$ 4,327	$ 15,377	$ 3,192	37,411	26,991	12,003
Amount Reclassified from AOCI
Comprehensive Income
Net income									723	(352)	16
Available-for-sale securities | Amount Reclassified from AOCI
Comprehensive Income
Gain (loss) on sale of available-for-sale securities, net									914	(166)	327
Income from continuing operations, before income taxes									914	(166)	327
Income tax expense									(214)	44	(88)
Net income									700	(122)	239
Defined benefit pension plan items | Amount Reclassified from AOCI
Comprehensive Income
Salaries and employee benefits									(420)	(271)	(306)
Income from continuing operations, before income taxes									(420)	(271)	(306)
Income tax expense									98	73	83
Net income									(322)	(198)	(223)
Investment hedge | Amount Reclassified from AOCI
Comprehensive Income
Interest on investment securities									473	(44)	0
Income from continuing operations, before income taxes									473	(44)	0
Income tax expense									(128)	12	0
Net income									$ 345	$ (32)	$ 0