RECENTLY ADOPTED AND ISSUED ACCOUNTING STANDARDS (Details) - USD ($) $ in Thousands		9 Months Ended
	Jan. 01, 2020	Sep. 30, 2020		Jun. 30, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	$ 119,155	$ 168,544	[1]	$ 158,661	$ 57,650	[1]	$ 56,552	$ 61,549	$ 56,542
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	61,505	61,505
Deferred Tax Liabilities, Deferred Expense	16,252				33,030
Deferred tax liability, Credit Loss, Change in Method, Credit Loss Expense (Reversal)	(16,778)
Off-Balance Sheet, Credit Loss, Liability	12,740				585
Off-Balance Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal)	12,155
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	28,485	50,516		50,421	18,584		18,240	24,586	18,746
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	9,901	9,901
Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	1,089	1,287		1,431	971		1,005	1,393	1,130
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	118	118
Construction real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	13,960	18,970		15,357	2,381		2,767	2,919	3,413
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	11,579	11,579
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	47,697	72,207		62,340	23,579		21,853	20,357	21,048
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	24,118	24,118
Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	10,789	9,286		10,581	5,299		5,496	5,008	4,964
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	5,490	5,490
Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	13,217	12,530		14,236	4,787		5,083	5,307	5,348
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	8,430	8,430
Installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	1,193	1,237		1,226	392		421	395	362
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	801	801
Credit card
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Allowance	2,725	2,511		$ 3,069	$ 1,657		$ 1,687	$ 1,584	$ 1,531
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	$ 1,068	$ 1,068

[1] Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.