INVESTMENT SECURITIES - Narrative (Details)	3 Months Ended
Mar. 31, 2021 USD ($) position	Mar. 31, 2020 USD ($)
Investments, Debt and Equity Securities [Abstract]
Maximum individual state general bond obligation as a percentage of total debt securities (percent)	1.00%
Securities in unrealized loss positions, number of positions	415
Securities, number of positions	1,735
Recognized gain (loss) related to equity securities \| $	$ (85,000,000)	$ 0
S&P AA- rating
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of debt securities considered to be of investment-grade (percent)	96.00%

Debt Securities, Available-for-sale, Securities, Number Of Positions

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- Definition

Maximum Individual State General Bond Obligation, As Percentage Of Total Debt Securities

+ References

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- Definition

Percentage Of Total Debt Securities, Investment Grade Quality

+ References

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- Definition

Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922888-210455

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- Definition

Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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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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