DERIVATIVES - Disclosure by Type of Financial Instrument (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	$ 238,050	$ 272,606
Derivative Liability, Fair Value, Gross Asset	(281,893)	(402,480)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(43,843)	(129,874)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	125,513	184,991
Derivative Liability, Fair Value, Gross Asset	(223,880)	(385,088)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(98,367)	(200,097)
Fair Value Hedges | Foreign Exchange [Member] | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	112,537	87,615
Derivative Liability, Fair Value, Gross Asset	(58,013)	(17,392)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 54,524	$ 70,223