LEASES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2018
Leases [Abstract]
Lessee, Operating Lease, Description	The Company leases real estate properties for its network of bank branches, financial centers and corporate offices. All of the Company’s leases are currently classified as operating.
Lessee, Operating Lease, Option to Extend	Most lease agreements include one or more options to renew, with renewal terms that can extend the original lease term from one to twenty years or more.
Operating Lease, Right-of-Use Asset	$ 69,300,000	$ 77,700,000
Operating Lease, Liability	76,871,000	$ 85,100,000
Operating Lease Expense	11,300,000
ROU assets obtained in exchange for operating lease obligations	400,000
Cash paid for amounts included in the measurement of lease liabilities	$ 8,700,000
Weighted average remaining lease term	10 years 4 months 24 days
Weighted average discount rate	3.28%
Lease obligations related to finance and operating leases incurred	$ 0