DERIVATIVES - Interest Rate Swaps Designated as Cash Flow Hedges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivatives
Notional amounts	$ 823,900	$ 193,400
Interest rate swaps | Derivative designated as a cash flow hedge
Derivatives
Notional amounts	$ 290,000	$ 240,000
Weighted average pay rates (as a percent)	1.84%	1.84%
Weighted average receive rates (as a percent)	1.94%	2.77%
Weighted average maturity	2 years 10 months 28 days	2 years 11 days