DERIVATIVES - Derivative Financial Instruments, Average Remaining Maturity and the Weighted-Average Interest Rates being Paid and Received (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative, Notional Amount	$ 16,383,398	$ 11,875,690
Derivative Asset	237,958	272,499
Derivative Liability	$ (238,050)	(272,606)
Average Maturity (years)	2 years 1 month 6 days
Fair Value	$ (92)
Interest Rate Swap \| Derivative Financial Instruments Receive Fixed Pay Variable
Derivative [Line Items]
Derivative, Notional Amount	$ 2,301,210
Average Maturity (years)	6 years
Fair Value	$ 117,353
Interest Rate Swap \| Derivative Financial Instruments Receive Variable Pay Fixed
Derivative [Line Items]
Derivative, Notional Amount	$ 2,301,210
Average Maturity (years)	6 years
Fair Value	$ (117,445)
Foreign Exchange [Member] \| Derivative Financial Instruments Receive Fixed Pay Variable
Derivative [Line Items]
Derivative, Notional Amount	$ 5,890,489
Average Maturity (years)	7 months 6 days
Fair Value	$ 18,217
Foreign Exchange [Member] \| Derivative Financial Instruments Receive Variable Pay Fixed
Derivative [Line Items]
Derivative, Notional Amount	$ 5,890,489
Average Maturity (years)	7 months 6 days
Fair Value	$ (18,217)
Accrued interest and other assets \| Fair Value Hedges \| Matched interest rate swaps
Derivative [Line Items]
Derivative, Notional Amount	2,301,210	2,300,336
Derivative Asset	121,387	184,777
Derivative Liability	(4,034)	(107)
Accrued interest and other assets \| Foreign Exchange [Member] \| Matched interest rate swaps
Derivative [Line Items]
Derivative, Notional Amount	5,890,489	3,637,509
Derivative Asset	65,377	60,366
Derivative Liability	(47,160)	(27,249)
Accrued interest and other liabilities \| Fair Value Hedges \| Matched interest rate swaps
Derivative [Line Items]
Derivative, Notional Amount	2,301,210	2,300,336
Derivative Asset	4,034	107
Derivative Liability	(121,479)	(184,884)
Accrued interest and other liabilities \| Foreign Exchange [Member] \| Matched interest rate swaps
Derivative [Line Items]
Derivative, Notional Amount	5,890,489	3,637,509
Derivative Asset	47,160	27,249
Derivative Liability	$ (65,377)	$ (60,366)

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Nominal or face amount used to calculate payment on derivative.

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