FAIR VALUE DISCLOSURES AND REPORTING, THE FAIR VALUE OPTION AND FAIR VALUE MEASUREMENTS - Reconciliation of Activity for Assets Measured at Fair Value based on Significant Unobservable (Non-market) Information (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Bank-Issued Trust Preferred Securities
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, January 1	$ 408	$ 874
Paydown	(273)
Unrealized gain/(loss) included in comprehensive income	106	(466)
Balance at September 30, 2020 and December 31, 2019	241	408
Municipal securities
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, January 1	10,345	7,574
Unrealized gain/(loss) included in comprehensive income	4,912	2,771
Balance at September 30, 2020 and December 31, 2019	$ 15,257	$ 10,345