LOANS, Amount of Business Lending Loans by Credit Quality Category (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans	$ 7,528,039	$ 6,890,543
Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		5,450,592
Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,439,951
Business Lending [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	670,379
2019	405,722
2018	395,076
2017	294,450
2016	308,151
Prior	746,224
Revolving loans amortized cost basis	635,341
Total	3,455,343
Loans		2,775,876
Business Lending [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,856,585
Business Lending [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		919,291
Business Lending [Member] | Pass [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	661,019
2019	390,621
2018	371,073
2017	273,598
2016	274,860
Prior	634,379
Revolving loans amortized cost basis	567,034
Total	3,172,584
Loans		2,487,973
Business Lending [Member] | Pass [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,655,280
Business Lending [Member] | Pass [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		832,693
Business Lending [Member] | Special Mention [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	6,026
2019	12,045
2018	6,641
2017	12,701
2016	18,005
Prior	56,168
Revolving loans amortized cost basis	30,485
Total	142,071
Loans		144,277
Business Lending [Member] | Special Mention [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		98,953
Business Lending [Member] | Special Mention [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		45,324
Business Lending [Member] | Classified [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	3,334
2019	3,056
2018	17,362
2017	8,151
2016	15,286
Prior	55,677
Revolving loans amortized cost basis	37,822
Total	140,688
Loans		131,829
Business Lending [Member] | Classified [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		102,352
Business Lending [Member] | Classified [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		29,477
Business Lending [Member] | Doubtful [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Total	0
Loans		0
Business Lending [Member] | Doubtful [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		0
Business Lending [Member] | Doubtful [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		0
Business Lending [Member] | Acquired Impaired [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		11,797
Business Lending [Member] | Acquired Impaired [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		0
Business Lending [Member] | Acquired Impaired [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		11,797
All Other Loans [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		3,594,007
All Other Loans [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		520,660
All Other Loans [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		3,579,851
All Other Loans [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		517,264
All Other Loans [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		14,156
All Other Loans [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		3,396
Consumer Mortgage [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	158,861
2019	356,457
2018	273,486
2017	269,787
2016	271,965
Prior	1,087,278
Revolving loans amortized cost basis	10,226
Total	2,428,060
Consumer Mortgage [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,996,716
Consumer Mortgage [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		434,186
Consumer Mortgage [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,984,533
Consumer Mortgage [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		431,523
Consumer Mortgage [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		12,183
Consumer Mortgage [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		2,663
Consumer Mortgage [Member] | FICO AB [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	111,491
2019	247,801
2018	186,837
2017	185,472
2016	178,776
Prior	715,498
Revolving loans amortized cost basis	454
Total	1,626,329
Consumer Mortgage [Member] | FICO AB [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	111,491
2019	247,646
2018	186,686
2017	185,064
2016	178,459
Prior	712,049
Revolving loans amortized cost basis	454
Total	1,621,849
Consumer Mortgage [Member] | FICO AB [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	0
2019	155
2018	151
2017	408
2016	317
Prior	3,449
Revolving loans amortized cost basis	0
Total	4,480
Consumer Mortgage [Member] | FICO CDE [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	47,370
2019	108,656
2018	86,649
2017	84,315
2016	93,189
Prior	371,780
Revolving loans amortized cost basis	9,772
Total	801,731
Consumer Mortgage [Member] | FICO CDE [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	47,370
2019	108,296
2018	85,917
2017	83,641
2016	91,733
Prior	362,287
Revolving loans amortized cost basis	9,772
Total	789,016
Consumer Mortgage [Member] | FICO CDE [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	0
2019	360
2018	732
2017	674
2016	1,456
Prior	9,493
Revolving loans amortized cost basis	0
Total	12,715
Consumer Indirect [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	135,342
2019	372,460
2018	260,805
2017	118,294
2016	88,691
Prior	81,273
Revolving loans amortized cost basis	0
Total	1,056,865
Consumer Indirect [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,107,308
Consumer Indirect [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		5,754
Consumer Indirect [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	135,333
2019	372,290
2018	260,629
2017	118,119
2016	88,554
Prior	81,194
Revolving loans amortized cost basis	0
Total	1,056,119
Consumer Indirect [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,107,183
Consumer Indirect [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		5,723
Consumer Indirect [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	9
2019	170
2018	176
2017	175
2016	137
Prior	79
Revolving loans amortized cost basis	0
Total	746
Consumer Indirect [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		125
Consumer Indirect [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		31
Consumer Direct [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	27,668
2019	60,989
2018	38,371
2017	18,594
2016	8,888
Prior	7,892
Revolving loans amortized cost basis	6,826
Total	169,228
Consumer Direct [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		175,976
Consumer Direct [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		8,402
Consumer Direct [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	27,668
2019	60,954
2018	38,348
2017	18,528
2016	8,888
Prior	7,892
Revolving loans amortized cost basis	6,824
Total	169,102
Consumer Direct [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		175,900
Consumer Direct [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		8,350
Consumer Direct [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	0
2019	35
2018	23
2017	66
2016	0
Prior	0
Revolving loans amortized cost basis	2
Total	126
Consumer Direct [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		76
Consumer Direct [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		52
Home Equity [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	31,060
2019	53,585
2018	31,703
2017	26,759
2016	21,996
Prior	41,082
Revolving loans amortized cost basis	212,358
Total	418,543
Home Equity [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		314,007
Home Equity [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		72,318
Home Equity [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	31,060
2019	53,585
2018	31,703
2017	26,694
2016	21,831
Prior	40,438
Revolving loans amortized cost basis	210,726
Total	416,037
Home Equity [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		312,235
Home Equity [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		71,668
Home Equity [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
2020	0
2019	0
2018	0
2017	65
2016	165
Prior	644
Revolving loans amortized cost basis	1,632
Total	$ 2,506
Home Equity [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		1,772
Home Equity [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year [Abstract]
Loans		$ 650