LOANS, Amount of Business Lending Loans by Credit Quality Category (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Business Lending Loans by Credit Quality Category [Abstract]
Loans	$ 6,284,070	$ 6,281,121
Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	5,132,779	5,027,984
Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,151,291	1,253,137
Business Lending [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,395,684	2,396,977
Business Lending [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,678,604	1,618,827
Business Lending [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	717,080	778,150
Business Lending [Member] | Pass [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,136,870	2,141,830
Business Lending [Member] | Pass [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,510,549	1,439,337
Business Lending [Member] | Pass [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	626,321	702,493
Business Lending [Member] | Special Mention [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	145,842	145,172
Business Lending [Member] | Special Mention [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	87,398	105,065
Business Lending [Member] | Special Mention [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	58,444	40,107
Business Lending [Member] | Classified [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	109,325	102,950
Business Lending [Member] | Classified [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	80,657	74,425
Business Lending [Member] | Classified [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	28,668	28,525
Business Lending [Member] | Doubtful [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	0	1,579
Business Lending [Member] | Doubtful [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	0	0
Business Lending [Member] | Doubtful [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	0	1,579
Business Lending [Member] | Acquired Impaired [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,647	5,446
Business Lending [Member] | Acquired Impaired [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	0	0
Business Lending [Member] | Acquired Impaired [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,647	5,446
All Other Loans [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,454,175	3,409,157
All Other Loans [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	434,211	474,987
All Other Loans [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,440,360	3,395,920
All Other Loans [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	431,437	471,774
All Other Loans [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	13,815	13,237
All Other Loans [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,774	3,213
Consumer Mortgage [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,897,647	1,848,450
Consumer Mortgage [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	358,135	386,958
Consumer Mortgage [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,885,486	1,837,185
Consumer Mortgage [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	355,983	384,336
Consumer Mortgage [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	12,161	11,265
Consumer Mortgage [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,152	2,622
Consumer Indirect [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,074,947	1,072,392
Consumer Indirect [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	7,887	10,815
Consumer Indirect [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,074,790	1,072,134
Consumer Indirect [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	7,855	10,781
Consumer Indirect [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	157	258
Consumer Indirect [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	32	34
Consumer Direct [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	175,876	175,774
Consumer Direct [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,275	3,046
Consumer Direct [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	175,849	175,726
Consumer Direct [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,271	3,042
Consumer Direct [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	27	48
Consumer Direct [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	4	4
Home Equity [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	305,705	312,541
Home Equity [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	65,914	74,168
Home Equity [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	304,235	310,875
Home Equity [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	65,328	73,615
Home Equity [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,470	1,666
Home Equity [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	$ 586	$ 553