DERIVATIVES - Summary of Derivative Financial Instruments and Balances (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 226,782	$ 272,499
Derivative liabilities	226,891	272,606
Other Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Credit Risk Derivative Liabilities, at Fair Value		2,700
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Derivative Asset	10,317	107
Derivative liabilities	111,874	184,884
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other assets
Derivatives, Fair Value [Line Items]
Derivative Asset	111,765	184,777
Derivative liabilities	$ 10,317	$ 107