BORROWINGS - Schedule of Subordinated Debt (Details)	3 Months Ended
Mar. 31, 2022 USD ($)
Debt Instrument [Line Items]
Aggregate Principal Amount Issued	$ 583,000,000
Net Proceeds	586,000,000
Carrying Value	$ 573,000,000
2.20% Senior Notes due February 24, 2023
Debt Instrument [Line Items]
Interest Rate	2.20%
Aggregate Principal Amount Issued	$ 300,000,000
Net Proceeds	298,000,000
Carrying Value	$ 299,000,000
4.95% Fixed-To-Floating Rate Subordinated Notes due 2029
Debt Instrument [Line Items]
Interest Rate	4.95%
Aggregate Principal Amount Issued	$ 120,000,000
Net Proceeds	118,000,000
Carrying Value	$ 119,000,000
4.95% Fixed-To-Floating Rate Subordinated Notes due 2029 \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	2.40%
4.875% Subordinated Notes due 2025
Debt Instrument [Line Items]
Interest Rate	4.875%
Aggregate Principal Amount Issued	$ 100,000,000
Net Proceeds	98,000,000
Carrying Value	$ 99,000,000
7.625% Subordinated Notes due August 12, 2023
Debt Instrument [Line Items]
Interest Rate	7.625%
Aggregate Principal Amount Issued	$ 38,000,000
Net Proceeds	46,000,000
Carrying Value	$ 30,000,000
6.00% Fixed-To-Floating Rate Subordinated Notes due December 6, 2028
Debt Instrument [Line Items]
Interest Rate	6.00%
Aggregate Principal Amount Issued	$ 25,000,000
Net Proceeds	26,000,000
Carrying Value	$ 26,000,000
6.00% Fixed-To-Floating Rate Subordinated Notes due December 6, 2028 \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	3.02%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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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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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

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- Definition

The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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