LOANS, Amount of Business Lending Loans by Credit Quality Category (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Business Lending Loans by Credit Quality Category [Abstract]
Loans	$ 6,281,121	$ 6,256,757
Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	5,027,984	4,619,663
Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,253,137	1,637,094
Business Lending [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,396,977	2,424,223
Business Lending [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,618,827	1,376,599
Business Lending [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	778,150	1,047,624
Business Lending [Member] | Pass [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,141,830	2,134,137
Business Lending [Member] | Pass [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,439,337	1,170,156
Business Lending [Member] | Pass [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	702,493	963,981
Business Lending [Member] | Special Mention [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	145,172	166,397
Business Lending [Member] | Special Mention [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	105,065	129,076
Business Lending [Member] | Special Mention [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	40,107	37,321
Business Lending [Member] | Classified [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	102,950	111,995
Business Lending [Member] | Classified [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	74,425	77,367
Business Lending [Member] | Classified [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	28,525	34,628
Business Lending [Member] | Doubtful [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,579	1,579
Business Lending [Member] | Doubtful [Member] | Legacy Loan [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	1,579	1,579
Business Lending [Member] | Acquired Impaired [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	5,446	10,115
Business Lending [Member] | Acquired Impaired [Member] | Legacy Loan [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	5,446	10,115
All Other Loans [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,409,157	3,243,064
All Other Loans [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	474,987	589,470
All Other Loans [Member] | Performing [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,395,920	3,229,051
All Other Loans [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	471,774	584,874
All Other Loans [Member] | Nonperforming [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	13,237	14,013
All Other Loans [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,213	4,596
Consumer Mortgage [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,848,450	1,754,609
Consumer Mortgage [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	386,958	465,689
Consumer Mortgage [Member] | Performing [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,837,185	1,742,387
Consumer Mortgage [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	384,336	462,597
Consumer Mortgage [Member] | Nonperforming [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	11,265	12,222
Consumer Mortgage [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,622	3,092
Consumer Indirect [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,072,392	991,836
Consumer Indirect [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	10,815	20,142
Consumer Indirect [Member] | Performing [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,072,134	991,541
Consumer Indirect [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	10,781	20,134
Consumer Indirect [Member] | Nonperforming [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	258	295
Consumer Indirect [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	34	8
Consumer Direct [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	175,774	174,479
Consumer Direct [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,046	5,450
Consumer Direct [Member] | Performing [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	175,726	174,431
Consumer Direct [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,042	5,450
Consumer Direct [Member] | Nonperforming [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	48	48
Consumer Direct [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	4	0
Home Equity [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	312,541	322,140
Home Equity [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	74,168	98,189
Home Equity [Member] | Performing [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	310,875	320,692
Home Equity [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	73,615	96,693
Home Equity [Member] | Nonperforming [Member] | Legacy Loan [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,666	1,448
Home Equity [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	$ 553	$ 1,496