BORROWINGS - Schedule of Junior Subordinated Debt Trusts (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 73	$ 72
Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	77
Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	3
F.N.B. Statutory Trust II
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22
Interest Rate	7.32%
F.N.B. Statutory Trust II | SOFR
Subordinated Borrowing [Line Items]
Basis points	1.65%
F.N.B. Statutory Trust II | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 22
F.N.B. Statutory Trust II | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	1
Yadkin Valley Statutory Trust I
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 23
Interest Rate	6.99%
Yadkin Valley Statutory Trust I | SOFR
Subordinated Borrowing [Line Items]
Basis points	1.32%
Yadkin Valley Statutory Trust I | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 25
Yadkin Valley Statutory Trust I | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	1
FNB Financial Services Capital Trust I
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 23
Interest Rate	7.12%
FNB Financial Services Capital Trust I | SOFR
Subordinated Borrowing [Line Items]
Basis points	1.46%
FNB Financial Services Capital Trust I | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 25
FNB Financial Services Capital Trust I | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	1
Patapsco Statutory Trust I
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 5
Interest Rate	7.15%
Patapsco Statutory Trust I | SOFR
Subordinated Borrowing [Line Items]
Basis points	1.48%
Patapsco Statutory Trust I | Trust Preferred Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 5
Patapsco Statutory Trust I | Common Securities
Subordinated Borrowing [Line Items]
Junior subordinated debt	$ 0