LOAN SERVICING - Activity in MSR (Details) - Mortgage Servicing Rights - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Servicing Assets at Fair Value [Line Items]
Mortgage loans sold with servicing retained	$ 5,094,000,000		$ 5,094,000,000		$ 4,855,000,000
Mortgage loans sold with servicing retained	315,000,000	$ 518,000,000	666,000,000	$ 1,024,000,000
Pretax net gains resulting from above loan sales	(7,000,000)	11,000,000	(7,000,000)	26,000,000
Mortgage servicing fees	3,000,000	3,000,000	6,000,000	6,000,000
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	48,500,000	38,600,000	44,400,000	35,600,000
Additions	4,000,000.0	5,700,000	8,100,000	10,900,000
Payoffs and curtailments	(1,400,000)	(3,500,000)	(3,000,000.0)	(7,600,000)
(Impairment charge) / recovery	200,000	300,000	2,500,000	2,800,000
Amortization	(600,000)	(600,000)	(1,300,000)	(1,200,000)
Balance at end of period	50,700,000	40,500,000	50,700,000	40,500,000
Fair value, start	58,200,000	40,200,000	46,000,000.0	35,600,000
Fair value, end	64,100,000	$ 40,800,000	64,100,000	$ 40,800,000
Valuation allowance for servicing rights	$ 0		$ 0		$ 2,500,000