LOANS AND LEASES - Loan Delinquency, including Nonaccrual Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 32,275	$ 27,942
Current	5,971,039	5,880,281
Loans and Leases Receivable, Gross	6,003,314	5,908,223
Purchased impaired loans	98,707	104,960
Total loans and leases	6,102,021	6,013,183
> 90 days past due and still accruing	529	62
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	5,213	6,896
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	9,325	3,179
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	17,737	17,867
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	7,579	7,490
Current	1,933,461	1,901,821
Loans and Leases Receivable, Gross	1,941,040	1,909,311
Purchased impaired loans	2,701	3,432
Total loans and leases	1,943,741	1,912,743
> 90 days past due and still accruing	0	0
Commercial | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,399	755
Commercial | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	4,857	1,657
Commercial | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,323	5,078
Lease financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	943	485
Current	80,674	88,862
Loans and Leases Receivable, Gross	81,617	89,347
Purchased impaired loans	0	0
Total loans and leases	81,617	89,347
> 90 days past due and still accruing	0	0
Lease financing | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	943	485
Lease financing | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Lease financing | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	234
Current	494,389	467,216
Loans and Leases Receivable, Gross	494,389	467,450
Purchased impaired loans	276	280
Total loans and leases	494,665	467,730
> 90 days past due and still accruing	0	0
Construction real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	234
Construction real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Construction real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	0	0
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	15,808	10,694
Current	2,475,106	2,419,969
Loans and Leases Receivable, Gross	2,490,914	2,430,663
Purchased impaired loans	53,137	59,428
Total loans and leases	2,544,051	2,490,091
> 90 days past due and still accruing	0	0
Commercial real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	236	1,716
Commercial real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,317	201
Commercial real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	12,255	8,777
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,197	3,329
Current	427,689	430,500
Loans and Leases Receivable, Gross	429,886	433,829
Purchased impaired loans	38,698	37,562
Total loans and leases	468,584	471,391
> 90 days past due and still accruing	0	0
Residential real estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	497	526
Residential real estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	341	811
Residential real estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,359	1,992
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	3,903	4,863
Current	476,446	485,127
Loans and Leases Receivable, Gross	480,349	489,990
Purchased impaired loans	3,294	3,614
Total loans and leases	483,643	493,604
> 90 days past due and still accruing	0	0
Home equity | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,395	2,716
Home equity | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	508	394
Home equity | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	2,000	1,753
Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	629	413
Current	38,018	40,529
Loans and Leases Receivable, Gross	38,647	40,942
Purchased impaired loans	601	644
Total loans and leases	39,248	41,586
> 90 days past due and still accruing	0	0
Installment | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	284	179
Installment | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	74	29
Installment | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	271	205
Credit card
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	1,216	434
Current	45,256	46,257
Loans and Leases Receivable, Gross	46,472	46,691
Purchased impaired loans	0	0
Total loans and leases	46,472	46,691
> 90 days past due and still accruing	529	62
Credit card | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	459	285
Credit card | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	228	87
Credit card | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	$ 529	$ 62