INVESTMENT SECURITIES - OTHER THAN TEMPORARY IMPAIRMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Bank's private label mortgage backed security credit losses recognized in earnings
Number of securities held	173	182
Available-for-sale debt securities	$ 471,355	$ 475,738
Private label mortgage backed security
Bank's private label mortgage backed security credit losses recognized in earnings
Number of securities held	1
Available-for-sale debt securities	$ 3,495	3,712
Rollforward of the Bank's private label mortgage backed security credit losses recognized in earnings
Balance, beginning of period	1,613	1,765	$ 1,765
Recovery of losses previously recorded	(151)	(152)	0
Balance, end of period	1,462	$ 1,613	$ 1,765
Additional impairment charge that may be recognized	$ 2,200