ALLOWANCE FOR LOAN AND LEASE LOSSES AND CREDIT QUALITY INFORMATION - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 9,322,559		$ 8,518,915
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,439,089
2019	573,197
2018	367,377
2017	246,242
2016	125,185
Prior	200,704
Revolving loans amortized cost basis	5,958
Revolving loans converted to term	172,602
Total Loans	3,130,354		2,286,351
Gross loans	2,902,815	$ 2,046,798
Commercial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,360,120
2019	460,904
2018	275,565
2017	182,326
2016	105,960
Prior	148,327
Revolving loans amortized cost basis	5,893
Revolving loans converted to term	139,851
Total Loans	2,678,946
Commercial | Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,514
2019	42,224
2018	29,414
2017	10,445
2016	8,145
Prior	29,059
Revolving loans amortized cost basis	0
Revolving loans converted to term	24,220
Total Loans	147,021
Commercial | Commercial and industrial | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	75,455
2019	70,069
2018	62,398
2017	53,471
2016	11,080
Prior	23,318
Revolving loans amortized cost basis	65
Revolving loans converted to term	8,531
Total Loans	304,387
Commercial | Owner-occupied commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	167,104
2019	264,938
2018	112,681
2017	182,864
2016	148,520
Prior	323,765
Revolving loans amortized cost basis	0
Revolving loans converted to term	144,622
Total Loans	1,344,494		1,273,408
Gross loans	1,344,494	1,296,466
Commercial | Owner-occupied commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	162,465
2019	236,745
2018	96,951
2017	151,118
2016	135,794
Prior	298,133
Revolving loans amortized cost basis	0
Revolving loans converted to term	134,165
Total Loans	1,215,371
Commercial | Owner-occupied commercial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	83
2019	7,974
2018	653
2017	17,670
2016	3,599
Prior	3,328
Revolving loans amortized cost basis	0
Revolving loans converted to term	3,451
Total Loans	36,758
Commercial | Owner-occupied commercial | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,556
2019	20,219
2018	15,077
2017	14,076
2016	9,127
Prior	22,304
Revolving loans amortized cost basis	0
Revolving loans converted to term	7,006
Total Loans	92,365
Commercial | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
2020	312,020
2019	326,177
2018	272,112
2017	329,720
2016	305,781
Prior	495,174
Revolving loans amortized cost basis	0
Revolving loans converted to term	126,524
Total Loans	2,167,508		2,271,985
Gross loans	2,167,508	2,222,976
Commercial | Commercial mortgages | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	277,281
2019	299,727
2018	247,892
2017	306,437
2016	301,239
Prior	462,444
Revolving loans amortized cost basis	0
Revolving loans converted to term	122,592
Total Loans	2,017,612
Commercial | Commercial mortgages | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,479
2019	7,211
2018	22,309
2017	21,450
2016	1,906
Prior	6,519
Revolving loans amortized cost basis	0
Revolving loans converted to term	1,861
Total Loans	69,735
Commercial | Commercial mortgages | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	26,260
2019	19,239
2018	1,911
2017	1,833
2016	2,636
Prior	26,211
Revolving loans amortized cost basis	0
Revolving loans converted to term	2,071
Total Loans	80,161
Commercial | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	123,965
2019	218,418
2018	214,989
2017	28,331
2016	7,711
Prior	3,947
Revolving loans amortized cost basis	0
Revolving loans converted to term	68,956
Total Loans	666,317		514,402
Gross loans	666,317	581,082
Commercial | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	123,965
2019	209,675
2018	214,989
2017	24,828
2016	7,711
Prior	3,864
Revolving loans amortized cost basis	0
Revolving loans converted to term	66,591
Total Loans	651,623
Commercial | Construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	3,503
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term	616
Total Loans	4,119
Commercial | Construction | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	8,743
2018	0
2017	0
2016	0
Prior	83
Revolving loans amortized cost basis	0
Revolving loans converted to term	1,749
Total Loans	10,575
Commercial | Paycheck Protection Program, CARES Act
Financing Receivable, Credit Quality Indicator [Line Items]
Gross loans	954,200
Residential
Financing Receivable, Credit Quality Indicator [Line Items]
2020	21,492
2019	32,628
2018	89,647
2017	103,019
2016	163,568
Prior	434,641
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	844,995		1,033,896
Gross loans	857,494	1,016,500
Residential | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	21,380
2019	32,628
2018	89,647
2017	103,019
2016	163,476
Prior	429,538
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	839,688
Residential | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	112
2019	0
2018	0
2017	0
2016	92
Prior	5,103
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	5,307
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	171,357
2019	152,211
2018	276,344
2017	72,107
2016	50,878
Prior	62,148
Revolving loans amortized cost basis	376,028
Revolving loans converted to term	7,818
Total Loans	1,168,891		$ 1,138,873
Gross loans	1,168,891	$ 1,128,731
Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	171,357
2019	152,211
2018	275,702
2017	71,871
2016	50,878
Prior	62,148
Revolving loans amortized cost basis	374,550
Revolving loans converted to term	7,439
Total Loans	1,166,156
Consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	642
2017	236
2016	0
Prior	0
Revolving loans amortized cost basis	1,478
Revolving loans converted to term	379
Total Loans	$ 2,735