ALLOWANCE FOR LOAN AND LEASE LOSSES AND CREDIT QUALITY INFORMATION - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 9,336,369		$ 8,601,678
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,309,860
2019	662,896
2018	385,746
2017	260,396
2016	149,627
Prior	232,713
Revolving loans amortized cost basis	6,399
Revolving loans converted to term	159,197
Total Loans	3,166,834		2,340,524
Gross loans	2,953,701	$ 2,046,798
Commercial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,249,900
2019	568,960
2018	310,071
2017	207,981
2016	135,074
Prior	176,408
Revolving loans amortized cost basis	6,368
Revolving loans converted to term	137,064
Total Loans	2,791,826
Commercial | Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,106
2019	24,940
2018	17,372
2017	7,703
2016	4,699
Prior	31,935
Revolving loans amortized cost basis	0
Revolving loans converted to term	16,089
Total Loans	103,844
Commercial | Commercial and industrial | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	58,854
2019	68,996
2018	58,303
2017	44,712
2016	9,854
Prior	24,370
Revolving loans amortized cost basis	31
Revolving loans converted to term	6,044
Total Loans	271,164
Commercial | Owner-occupied commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	97,539
2019	272,079
2018	119,770
2017	186,610
2016	154,182
Prior	350,921
Revolving loans amortized cost basis	0
Revolving loans converted to term	156,152
Total Loans	1,337,253		1,280,894
Gross loans	1,337,253	1,296,466
Commercial | Owner-occupied commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	95,721
2019	262,486
2018	112,582
2017	166,073
2016	144,973
Prior	340,010
Revolving loans amortized cost basis	0
Revolving loans converted to term	149,516
Total Loans	1,271,361
Commercial | Owner-occupied commercial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	311
2018	0
2017	11,585
2016	0
Prior	1,266
Revolving loans amortized cost basis	0
Revolving loans converted to term	1,848
Total Loans	15,010
Commercial | Owner-occupied commercial | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,818
2019	9,282
2018	7,188
2017	8,952
2016	9,209
Prior	9,645
Revolving loans amortized cost basis	0
Revolving loans converted to term	4,788
Total Loans	50,882
Commercial | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
2020	184,106
2019	342,667
2018	292,448
2017	336,035
2016	322,289
Prior	556,018
Revolving loans amortized cost basis	0
Revolving loans converted to term	131,984
Total Loans	2,165,547		2,246,047
Gross loans	2,165,547	2,222,976
Commercial | Commercial mortgages | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	163,925
2019	335,085
2018	291,054
2017	316,021
2016	317,738
Prior	530,844
Revolving loans amortized cost basis	0
Revolving loans converted to term	127,835
Total Loans	2,082,502
Commercial | Commercial mortgages | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	20,041
2019	6,276
2018	0
2017	15,857
2016	1,901
Prior	4,570
Revolving loans amortized cost basis	0
Revolving loans converted to term	1,870
Total Loans	50,515
Commercial | Commercial mortgages | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	140
2019	1,306
2018	1,394
2017	4,157
2016	2,650
Prior	20,604
Revolving loans amortized cost basis	0
Revolving loans converted to term	2,279
Total Loans	32,530
Commercial | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	90,202
2019	221,588
2018	220,350
2017	38,300
2016	6,156
Prior	4,289
Revolving loans amortized cost basis	0
Revolving loans converted to term	57,619
Total Loans	638,504		541,696
Gross loans	638,504	581,082
Commercial | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	90,202
2019	204,676
2018	220,350
2017	38,300
2016	6,156
Prior	4,201
Revolving loans amortized cost basis	0
Revolving loans converted to term	55,891
Total Loans	619,776
Commercial | Construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	8,137
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	8,137
Commercial | Construction | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	8,775
2018	0
2017	0
2016	0
Prior	88
Revolving loans amortized cost basis	0
Revolving loans converted to term	1,728
Total Loans	10,591
Commercial | Paycheck Protection Program, CARES Act
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	945,100
Residential
Financing Receivable, Credit Quality Indicator [Line Items]
2020	12,967
2019	35,388
2018	92,212
2017	112,961
2016	173,701
Prior	467,631
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	894,860		1,065,784
Gross loans	910,971	1,016,500
Residential | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	12,967
2019	35,388
2018	92,212
2017	112,961
2016	173,609
Prior	462,272
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	889,409
Residential | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	92
Prior	5,359
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	5,451
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	85,834
2019	165,512
2018	287,824
2017	81,090
2016	57,913
Prior	70,555
Revolving loans amortized cost basis	376,861
Revolving loans converted to term	7,782
Total Loans	1,133,371		$ 1,126,733
Gross loans	1,133,371	$ 1,128,731
Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	85,834
2019	165,512
2018	287,173
2017	80,871
2016	57,913
Prior	70,555
Revolving loans amortized cost basis	375,483
Revolving loans converted to term	7,392
Total Loans	1,130,733
Consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	651
2017	219
2016	0
Prior	0
Revolving loans amortized cost basis	1,378
Revolving loans converted to term	390
Total Loans	$ 2,638