LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Aged analysis of the company's loans [Abstract]
Total loans		$ 6,284,070	$ 6,281,121
Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		2,863	2,106
Nonaccrual		15,529	16,182
Total past due		45,548	53,387
Current		5,087,231	4,974,597
Total loans		5,132,779	5,027,984
Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		27,156	35,099
Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		184	349
Nonaccrual		5,884	6,362
Total past due		9,168	9,332
Acquired impaired	[1]	3,647	5,446
Current		1,138,476	1,238,359
Total loans		1,151,291	1,253,137
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		3,100	2,621
Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,395,684	2,396,977
Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,678,604	1,618,827
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		717,080	778,150
Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,897,647	1,848,450
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		358,135	386,958
Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,074,947	1,072,392
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		7,887	10,815
Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		175,876	175,774
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,275	3,046
Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		305,705	312,541
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		65,914	74,168
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,395,684	2,396,977
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		491	179
Nonaccrual		4,086	4,872
Total past due		8,835	10,312
Current		1,669,769	1,608,515
Total loans		1,678,604	1,618,827
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		4,258	5,261
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		0	0
Nonaccrual		3,294	3,498
Total past due		4,313	4,472
Acquired impaired	[1]	3,647	5,446
Current		709,120	768,232
Total loans		717,080	778,150
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,019	974
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,255,782	2,235,408
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		2,082	1,393
Nonaccrual		10,079	9,872
Total past due		21,836	23,733
Current		1,875,811	1,824,717
Total loans		1,897,647	1,848,450
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		9,675	12,468
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		80	232
Nonaccrual		2,072	2,390
Total past due		3,434	3,463
Acquired impaired	[1]	0	0
Current		354,701	383,495
Total loans		358,135	386,958
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,282	841
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,082,834	1,083,207
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		157	258
Nonaccrual		0	0
Total past due		11,130	14,867
Current		1,063,817	1,057,525
Total loans		1,074,947	1,072,392
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		10,973	14,609
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		32	34
Nonaccrual		0	0
Total past due		65	112
Acquired impaired	[1]	0	0
Current		7,822	10,703
Total loans		7,887	10,815
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		33	78
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans [Abstract]
Total loans		178,151	178,820
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		27	48
Nonaccrual		0	0
Total past due		1,144	1,826
Current		174,732	173,948
Total loans		175,876	175,774
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,117	1,778
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		4	4
Nonaccrual		0	0
Total past due		44	119
Acquired impaired	[1]	0	0
Current		2,231	2,927
Total loans		2,275	3,046
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		40	115
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans [Abstract]
Total loans		371,619	386,709
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		106	228
Nonaccrual		1,364	1,438
Total past due		2,603	2,649
Current		303,102	309,892
Total loans		305,705	312,541
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,133	983
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		68	79
Nonaccrual		518	474
Total past due		1,312	1,166
Acquired impaired	[1]	0	0
Current		64,602	73,002
Total loans		65,914	74,168
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		$ 726	$ 613

[1] Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30.  As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans.