LOAN SERVICING - Activity in MSR (Details) - Mortgage Servicing Rights - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Servicing Assets at Fair Value [Line Items]
Mortgage loans sold with servicing retained	$ 5,160,000,000		$ 5,160,000,000		$ 4,855,000,000
Mortgage loans sold with servicing retained	204,000,000	$ 382,000,000	870,000,000	$ 1,406,000,000
Pre-tax net (losses) gains resulting from above loan sales	(2,000,000)	10,000,000	(9,000,000)	36,000,000
Mortgage servicing fees	3,000,000	3,000,000	9,000,000	9,000,000
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	50,700,000	40,500,000	44,400,000	35,600,000
Additions	2,400,000	4,400,000	10,500,000	15,300,000
Payoffs and curtailments	(800,000)	(2,800,000)	(3,800,000)	(10,400,000)
(Impairment charge) / recovery	0	1,000,000.0	2,500,000	3,800,000
Amortization	(600,000)	(600,000)	(1,900,000)	(1,800,000)
Balance at end of period	51,700,000	42,500,000	51,700,000	42,500,000
Fair value, start	64,100,000	40,800,000	46,000,000.0	35,600,000
Fair value, end	69,600,000	$ 43,200,000	69,600,000	$ 43,200,000
Valuation allowance for servicing rights	$ 0		$ 0		$ 2,500,000