LEASES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Lessee, Operating Lease, Description		The Company leases real estate properties for its network of bank branches, financial centers and corporate offices.
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	$ 71,300	$ 71,300	$ 77,700
Operating Lease Liability	78,799	78,799	$ 85,100
Operating Lease, Expense	2,900	8,600
ROU asset obtained in exchange for lease obligations	400
Cash paid for amounts included in the measurement of lease liabilities	$ 2,400	$ 6,700
Weighted average remaining lease term	10 years 7 months 6 days	10 years 7 months 6 days
Weighted average discount rate	3.29%	3.29%