RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jun. 30, 2018	Sep. 30, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Operating Lease, Right-of-Use Asset			$ 61,500		$ 60,200
Operating Lease, Liability			67,025		$ 65,800
Debt Securities, Held-to-maturity, Transfer, Amount	$ 268,700	$ 367,900
Realized gain (loss) on debt securities transferred from HTM to AFS	$ 200
Loans and Leases Receivable, Allowance		$ 54,076	$ 56,552	$ 61,549		$ 56,542	$ 57,715	$ 54,021
Allowance for loans and leases losses, range of increase, minimum			1.12%
Allowance for loans and leases losses, increase, maximum			1.32%