LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Aged analysis of the company's loans [Abstract]
Total loans		$ 6,361,300	$ 4,948,562
Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		1,640	1,963
Nonaccrual		14,359	16,600
Total past due		47,590	50,545
Current		4,459,658	4,402,657
Total loans		4,507,248	4,453,202
Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		31,591	31,982
Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		242	1,113
Nonaccrual		6,674	4,019
Total past due		15,429	8,439
Acquired impaired	[1]	14,781	5,553
Current		1,823,842	481,368
Total loans		1,854,052	495,360
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		8,513	3,307
Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,698,844	1,659,760
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		512,568	159,941
Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,479,152	1,490,076
Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,285,042	1,277,666
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,194,110	212,410
Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,030,747	1,014,825
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		26,917	30,147
Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		177,714	181,922
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		7,875	9,893
Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		314,901	319,029
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		112,582	82,969
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,211,412	1,819,701
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		946	1,180
Nonaccrual		10,291	11,352
Total past due		21,090	23,911
Current		1,677,754	1,635,849
Total loans		1,698,844	1,659,760
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		9,853	11,379
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		195	205
Nonaccrual		3,839	2,332
Total past due		6,036	4,076
Acquired impaired	[1]	0	0
Current		506,532	155,865
Total loans		512,568	159,941
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		2,002	1,539
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,479,152	1,490,076
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		527	145
Nonaccrual		2,664	3,811
Total past due		9,783	7,877
Current		1,275,259	1,269,789
Total loans		1,285,042	1,277,666
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		6,592	3,921
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		1,701	1,252
Total past due		6,984	1,780
Acquired impaired	[1]	14,781	5,553
Current		1,172,345	205,077
Total loans		1,194,110	212,410
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		5,283	528
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,057,664	1,044,972
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		115	166
Nonaccrual		0	0
Total past due		12,887	14,049
Current		1,017,860	1,000,776
Total loans		1,030,747	1,014,825
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		12,772	13,883
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		3	3
Nonaccrual		0	0
Total past due		174	234
Acquired impaired	[1]	0	0
Current		26,743	29,913
Total loans		26,917	30,147
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		171	231
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans [Abstract]
Total loans		185,589	191,815
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		31	58
Nonaccrual		0	0
Total past due		1,522	1,607
Current		176,192	180,315
Total loans		177,714	181,922
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		1,491	1,549
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		0	0
Nonaccrual		0	0
Total past due		149	231
Acquired impaired	[1]	0	0
Current		7,726	9,662
Total loans		7,875	9,893
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		149	231
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans [Abstract]
Total loans		427,483	401,998
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		21	414
Nonaccrual		1,404	1,437
Total past due		2,308	3,101
Current		312,593	315,928
Total loans		314,901	319,029
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		883	1,250
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		44	905
Nonaccrual		1,134	435
Total past due		2,086	2,118
Acquired impaired	[1]	0	0
Current		110,496	80,851
Total loans		112,582	82,969
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		$ 908	$ 778

[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.