LEASES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 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	$ 73,100	$ 73,100	$ 77,700
Operating Lease Liability	80,615	80,615	$ 85,100
Operating Lease, Expense	2,800	5,700
Cash paid for amounts included in the measurement of lease liabilities	$ 2,200	$ 4,300
Weighted average remaining lease term	10 years 8 months 12 days	10 years 8 months 12 days
Weighted average discount rate	3.31%	3.31%