DERIVATIVES - Disclosure by Type of Financial Instrument (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	$ 226,891	$ 272,606
Derivative Liability, Fair Value, Gross Asset	(259,256)	(402,480)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(32,365)	(129,874)
Fair Value Hedges \| Matched interest rate swaps \| Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	122,191	184,991
Derivative Liability, Fair Value, Gross Asset	(249,003)	(385,088)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(126,812)	(200,097)
Fair Value Hedges \| Foreign Exchange [Member] \| Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Gross amounts of recognized liabilities	104,700	87,615
Derivative Liability, Fair Value, Gross Asset	(10,253)	(17,392)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 94,447	$ 70,223

Fair value, after offset of derivative liability, of 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, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226006-175313

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant