DERIVATIVES - Non-Designated Hedges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivatives
Notional amounts	$ 1,100,000	$ 823,900
Loan Swap Fees	3,742	7,460	$ 716
Loan customers
Derivatives
Notional amounts	548,500	411,900
Bank counterparties
Derivatives
Notional amounts	548,500	411,900
Interest rate swaps | Non-Designated Hedges
Derivatives
Notional amounts	$ 1,097,100	$ 823,894
Weighted average pay rates (as a percent)	2.94%	3.75%
Weighted average receive rates (as a percent)	2.94%	3.75%
Weighted average maturity	10 years 7 days	10 years 9 months 7 days
Fair value of combined interest rate swaps	$ 0	$ 0