ALLOWANCE FOR CREDIT LOSSES, NONACCRUAL LOANS AND LEASES, AND CONCENTRATIONS OF CREDIT RISK - Modified (Details)	3 Months Ended
	Mar. 31, 2023 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 184,000,000
Total as a % of Loan Class	0.12%
Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 153,000,000
30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	4,000,000
60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	25,000,000
Unfunded loan commitment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	12,000,000
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 152,000,000
Total as a % of Loan Class	0.19%
Commercial | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 131,000,000
Commercial | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	21,000,000
Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 97,000,000
Total as a % of Loan Class	0.19%
Weighted-Average Interest Rate Reduction	4.05%
Weighted-Average Term Extension (in Months)	9 months
Weighted-Average Payment Deferral	$ 658,467
Commercial | Commercial and industrial | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	76,000,000
Commercial | Commercial and industrial | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Commercial and industrial | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Commercial and industrial | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Commercial and industrial | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	21,000,000
Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 55,000,000
Total as a % of Loan Class	0.19%
Weighted-Average Interest Rate Reduction	0.00%
Weighted-Average Term Extension (in Months)	14 months
Weighted-Average Payment Deferral	$ 0
Commercial | Commercial real estate | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	55,000,000
Commercial | Commercial real estate | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Commercial real estate | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Commercial real estate | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Commercial real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 0
Total as a % of Loan Class	0.00%
Weighted-Average Interest Rate Reduction	0.00%
Weighted-Average Term Extension (in Months)	0 months
Weighted-Average Payment Deferral	$ 0
Commercial | Leases | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Leases | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Leases | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Leases | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Commercial | Leases | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 32,000,000
Total as a % of Loan Class	0.04%
Retail | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 22,000,000
Retail | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	4,000,000
Retail | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Retail | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	4,000,000
Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 24,000,000
Total as a % of Loan Class	0.08%
Weighted-Average Interest Rate Reduction	1.47%
Weighted-Average Term Extension (in Months)	44 months
Weighted-Average Payment Deferral	$ 0
Retail | Residential mortgages | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	16,000,000
Retail | Residential mortgages | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	4,000,000
Retail | Residential mortgages | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Residential mortgages | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Retail | Residential mortgages | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 3,000,000
Total as a % of Loan Class	0.02%
Weighted-Average Interest Rate Reduction	2.02%
Weighted-Average Term Extension (in Months)	139 months
Weighted-Average Payment Deferral	$ 3,863
Retail | Home equity | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	1,000,000
Retail | Home equity | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Home equity | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Home equity | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Home equity | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 0
Total as a % of Loan Class	0.00%
Weighted-Average Interest Rate Reduction	2.76%
Weighted-Average Term Extension (in Months)	23 months
Weighted-Average Payment Deferral	$ 1,005
Retail | Automobile | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Automobile | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Automobile | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Automobile | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Automobile | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 2,000,000
Total as a % of Loan Class	0.02%
Weighted-Average Interest Rate Reduction	5.77%
Weighted-Average Term Extension (in Months)	0 months
Weighted-Average Payment Deferral	$ 3,037
Retail | Education | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Retail | Education | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Education | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Education | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Education | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 3,000,000
Total as a % of Loan Class	0.06%
Weighted-Average Interest Rate Reduction	17.79%
Weighted-Average Term Extension (in Months)	22 months
Weighted-Average Payment Deferral	$ 0
Retail | Other retail | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	3,000,000
Retail | Other retail | 30-59
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Other retail | 60-89
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Other retail | 90+
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Retail | Other retail | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	6,000,000
Interest Rate Reduction | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction | Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction | Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	6,000,000
Interest Rate Reduction | Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Interest Rate Reduction | Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction | Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction | Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	1,000,000
Interest Rate Reduction | Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	3,000,000
Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	119,000,000
Term Extension | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	99,000,000
Term Extension | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	44,000,000
Term Extension | Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	55,000,000
Term Extension | Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	20,000,000
Term Extension | Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	19,000,000
Term Extension | Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	1,000,000
Term Extension | Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension | Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension | Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Delay
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	33,000,000
Payment Delay | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	32,000,000
Payment Delay | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	32,000,000
Payment Delay | Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Delay | Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Delay | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	1,000,000
Payment Delay | Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Delay | Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Delay | Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Delay | Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	1,000,000
Payment Delay | Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Principal Forgiveness | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Principal Forgiveness | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	0
Principal Forgiveness | Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	0
Principal Forgiveness | Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	0
Principal Forgiveness | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Principal Forgiveness | Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	0
Principal Forgiveness | Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	0
Principal Forgiveness | Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	2,702
Principal Forgiveness | Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	0
Principal Forgiveness | Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Amount of Principal Forgiven	1,156,256
Interest Rate Reduction and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	5,000,000
Interest Rate Reduction and Term Extension | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction and Term Extension | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction and Term Extension | Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction and Term Extension | Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction and Term Extension | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	5,000,000
Interest Rate Reduction and Term Extension | Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	3,000,000
Interest Rate Reduction and Term Extension | Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	2,000,000
Interest Rate Reduction and Term Extension | Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction and Term Extension | Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Interest Rate Reduction and Term Extension | Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	21,000,000
Term Extension and Payment Delay | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	21,000,000
Term Extension and Payment Delay | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	21,000,000
Term Extension and Payment Delay | Commercial | Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Commercial | Leases
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Term Extension and Payment Delay | Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	0
Payment Discharged Due To Chapter 7 Bankruptcy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized cost basis	$ 7,000,000