ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in the Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Allowance for loan and lease losses:
Balance at beginning of period	$ 54,021	$ 57,961
Provision for loan and lease losses	2,303	367
Loans charged-off	(3,669)	(2,750)
Recoveries	1,725	748
Total net charge-offs	1,944	2,002
Balance at end of period	54,380	56,326
Ending allowance on loans individually evaluated for impairment			$ 288	$ 779
Ending allowance on loans collectively evaluated for impairment			54,092	53,242
Ending allowance for loan and lease losses	54,380	57,961	54,380	54,021
Loans and Leases:
Ending balance of loans individually evaluated for impairment			45,226	41,627
Ending balance of loans collectively evaluated for impairment			6,056,795	5,971,556
Loans and Leases Receivable, Net of Deferred Income			6,102,021	6,013,183
Commercial
Allowance for loan and lease losses:
Balance at beginning of period	17,598	19,225
Provision for loan and lease losses	889	(596)
Loans charged-off	(885)	(1,743)
Recoveries	436	262
Total net charge-offs	449	1,481
Balance at end of period	18,038	17,148
Ending allowance on loans individually evaluated for impairment			100	169
Ending allowance on loans collectively evaluated for impairment			17,938	17,429
Ending allowance for loan and lease losses	17,598	19,225	18,038	17,598
Loans and Leases:
Ending balance of loans individually evaluated for impairment			8,810	7,331
Ending balance of loans collectively evaluated for impairment			1,934,931	1,905,412
Loans and Leases Receivable, Net of Deferred Income			1,943,741	1,912,743
Lease financing
Allowance for loan and lease losses:
Balance at beginning of period	675	716
Provision for loan and lease losses	(49)	(100)
Loans charged-off	0	0
Recoveries	0	0
Total net charge-offs	0	0
Balance at end of period	626	616
Ending allowance on loans individually evaluated for impairment			0	0
Ending allowance on loans collectively evaluated for impairment			626	675
Ending allowance for loan and lease losses	626	716	626	675
Loans and Leases:
Ending balance of loans individually evaluated for impairment			0	82
Ending balance of loans collectively evaluated for impairment			81,617	89,265
Loans and Leases Receivable, Net of Deferred Income			81,617	89,347
Construction real estate
Allowance for loan and lease losses:
Balance at beginning of period	3,577	3,282
Provision for loan and lease losses	690	325
Loans charged-off	0	0
Recoveries	0	0
Total net charge-offs	0	0
Balance at end of period	4,267	3,607
Ending allowance on loans individually evaluated for impairment			0	0
Ending allowance on loans collectively evaluated for impairment			4,267	3,577
Ending allowance for loan and lease losses	4,267	3,282	4,267	3,577
Loans and Leases:
Ending balance of loans individually evaluated for impairment			26	29
Ending balance of loans collectively evaluated for impairment			494,639	467,701
Loans and Leases Receivable, Net of Deferred Income			494,665	467,730
Commercial real estate
Allowance for loan and lease losses:
Balance at beginning of period	20,930	26,540
Provision for loan and lease losses	815	(2,566)
Loans charged-off	(2,176)	(485)
Recoveries	752	256
Total net charge-offs	1,424	229
Balance at end of period	20,321	23,745
Ending allowance on loans individually evaluated for impairment			26	448
Ending allowance on loans collectively evaluated for impairment			20,295	20,482
Ending allowance for loan and lease losses	20,930	26,540	20,321	20,930
Loans and Leases:
Ending balance of loans individually evaluated for impairment			24,736	21,542
Ending balance of loans collectively evaluated for impairment			2,519,315	2,468,549
Loans and Leases Receivable, Net of Deferred Income			2,544,051	2,490,091
Residential real estate
Allowance for loan and lease losses:
Balance at beginning of period	4,683	3,208
Provision for loan and lease losses	114	2,329
Loans charged-off	(96)	(61)
Recoveries	26	9
Total net charge-offs	70	52
Balance at end of period	4,727	5,485
Ending allowance on loans individually evaluated for impairment			160	160
Ending allowance on loans collectively evaluated for impairment			4,567	4,523
Ending allowance for loan and lease losses	4,727	3,208	4,727	4,683
Loans and Leases:
Ending balance of loans individually evaluated for impairment			7,175	7,932
Ending balance of loans collectively evaluated for impairment			461,409	463,459
Loans and Leases Receivable, Net of Deferred Income			468,584	471,391
Home equity
Allowance for loan and lease losses:
Balance at beginning of period	4,935	3,043
Provision for loan and lease losses	(294)	805
Loans charged-off	(242)	(180)
Recoveries	429	106
Total net charge-offs	(187)	74
Balance at end of period	4,828	3,774
Ending allowance on loans individually evaluated for impairment			2	2
Ending allowance on loans collectively evaluated for impairment			4,826	4,933
Ending allowance for loan and lease losses	4,828	3,043	4,828	4,935
Loans and Leases:
Ending balance of loans individually evaluated for impairment			4,173	4,456
Ending balance of loans collectively evaluated for impairment			479,470	489,148
Loans and Leases Receivable, Net of Deferred Income			483,643	493,604
Installment
Allowance for loan and lease losses:
Balance at beginning of period	307	388
Provision for loan and lease losses	(49)	9
Loans charged-off	(16)	(49)
Recoveries	48	71
Total net charge-offs	(32)	(22)
Balance at end of period	290	419
Ending allowance on loans individually evaluated for impairment			0	0
Ending allowance on loans collectively evaluated for impairment			290	307
Ending allowance for loan and lease losses	307	388	290	307
Loans and Leases:
Ending balance of loans individually evaluated for impairment			306	255
Ending balance of loans collectively evaluated for impairment			38,942	41,331
Loans and Leases Receivable, Net of Deferred Income			39,248	41,586
Credit card
Allowance for loan and lease losses:
Balance at beginning of period	1,316	1,559
Provision for loan and lease losses	187	161
Loans charged-off	(254)	(232)
Recoveries	34	44
Total net charge-offs	(220)	(188)
Balance at end of period	1,283	1,532
Ending allowance on loans individually evaluated for impairment			0	0
Ending allowance on loans collectively evaluated for impairment			1,283	1,316
Ending allowance for loan and lease losses	$ 1,283	$ 1,559	1,283	1,316
Loans and Leases:
Ending balance of loans individually evaluated for impairment			0	0
Ending balance of loans collectively evaluated for impairment			46,472	46,691
Loans and Leases Receivable, Net of Deferred Income			$ 46,472	$ 46,691