BORROWINGS - Schedule of Subordinated Debt (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)
Debt Instrument [Line Items]
Aggregate Principal Amount Issued	$ 933,000,000	$ 933,000,000
Net Proceeds		933,000,000
Carrying Value	$ 921,000,000	$ 921,000,000
2.200% Senior Notes due February 24, 2023
Debt Instrument [Line Items]
Interest Rate	2.20%	2.20%
Aggregate Principal Amount Issued	$ 300,000,000	$ 300,000,000
Net Proceeds		298,000,000
Carrying Value	$ 300,000,000	$ 300,000,000
5.150% Senior Notes due August 25, 2025
Debt Instrument [Line Items]
Interest Rate	5.15%	5.15%
Aggregate Principal Amount Issued	$ 350,000,000	$ 350,000,000
Net Proceeds	347,400,000	347,000,000
Carrying Value	$ 347,000,000	$ 347,000,000
4.95% Fixed-To-Floating Rate Subordinated Notes due 2029
Debt Instrument [Line Items]
Interest Rate	4.95%	4.95%
Aggregate Principal Amount Issued	$ 120,000,000	$ 120,000,000
Net Proceeds		118,000,000
Carrying Value	$ 119,000,000	$ 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%	4.875%
Aggregate Principal Amount Issued	$ 100,000,000	$ 100,000,000
Net Proceeds		98,000,000
Carrying Value	$ 99,000,000	$ 99,000,000
7.625% Subordinated Notes due August 12, 2023
Debt Instrument [Line Items]
Interest Rate	7.625%	7.625%
Aggregate Principal Amount Issued	$ 38,000,000	$ 38,000,000
Net Proceeds		46,000,000
Carrying Value	$ 30,000,000	$ 30,000,000
6.00% Fixed-To-Floating Rate Subordinated Notes due December 6, 2028
Debt Instrument [Line Items]
Interest Rate	6.00%	6.00%
Aggregate Principal Amount Issued	$ 25,000,000	$ 25,000,000
Net Proceeds		26,000,000
Carrying Value	$ 26,000,000	$ 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%