ALLOWANCE FOR LOAN AND LEASE LOSSES AND CREDIT QUALITY INFORMATION - Credit Quality Indicators (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 8,534,986
Commercial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	191,086
2019	730,411
2018	473,093
2017	294,365
2016	171,549
Prior	273,189
Revolving loans amortized cost basis	6,971
Revolving loans converted to term	157,708
Total Loans	2,298,372
Commercial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	190,880
2019	694,130
2018	453,091
2017	286,737
2016	160,831
Prior	237,584
Revolving loans amortized cost basis	6,939
Revolving loans converted to term	152,139
Total Loans	2,182,331
Commercial | Commercial and industrial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	206
2019	0
2018	0
2017	560
2016	38
Prior	12,932
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	13,736
Commercial | Commercial and industrial | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	36,281
2018	20,002
2017	7,068
2016	10,680
Prior	22,673
Revolving loans amortized cost basis	32
Revolving loans converted to term	5,569
Total Loans	102,305
Commercial | Owner-occupied commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	35,698
2019	279,846
2018	122,443
2017	190,235
2016	156,884
Prior	371,777
Revolving loans amortized cost basis	0
Revolving loans converted to term	156,310
Total Loans	1,313,193
Commercial | Owner-occupied commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	34,334
2019	270,384
2018	115,803
2017	186,657
2016	149,168
Prior	362,582
Revolving loans amortized cost basis	0
Revolving loans converted to term	152,211
Total Loans	1,271,139
Commercial | Owner-occupied commercial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	0
Commercial | Owner-occupied commercial | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,364
2019	9,462
2018	6,640
2017	3,578
2016	7,716
Prior	9,195
Revolving loans amortized cost basis	0
Revolving loans converted to term	4,099
Total Loans	42,054
Commercial | Commercial mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
2020	89,915
2019	352,432
2018	352,644
2017	343,380
2016	347,963
Prior	607,446
Revolving loans amortized cost basis	0
Revolving loans converted to term	129,337
Total Loans	2,223,117
Commercial | Commercial mortgages | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	89,774
2019	351,122
2018	351,240
2017	321,439
2016	345,287
Prior	600,663
Revolving loans amortized cost basis	0
Revolving loans converted to term	127,042
Total Loans	2,186,567
Commercial | Commercial mortgages | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	16,091
2016	0
Prior	918
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	17,009
Commercial | Commercial mortgages | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	141
2019	1,310
2018	1,404
2017	5,850
2016	2,676
Prior	5,865
Revolving loans amortized cost basis	0
Revolving loans converted to term	2,295
Total Loans	19,541
Commercial | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	51,084
2019	216,257
2018	253,520
2017	49,438
2016	7,054
Prior	2,230
Revolving loans amortized cost basis	0
Revolving loans converted to term	46,670
Total Loans	626,253
Commercial | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	51,084
2019	216,257
2018	253,520
2017	49,438
2016	7,054
Prior	2,134
Revolving loans amortized cost basis	0
Revolving loans converted to term	46,670
Total Loans	626,157
Commercial | Construction | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	0
Commercial | Construction | Substandard or Lower
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	96
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	96
Residential
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,616
2019	38,158
2018	99,082
2017	125,502
2016	180,223
Prior	504,184
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	955,765
Residential | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,616
2019	38,158
2018	99,082
2017	125,502
2016	180,131
Prior	498,013
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	949,502
Residential | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	92
Prior	6,171
Revolving loans amortized cost basis	0
Revolving loans converted to term	0
Total Loans	6,263
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	20,145
2019	178,737
2018	277,620
2017	91,054
2016	64,239
Prior	87,021
Revolving loans amortized cost basis	391,425
Revolving loans converted to term	8,045
Total Loans	1,118,286
Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
2020	20,145
2019	178,737
2018	276,960
2017	90,890
2016	64,239
Prior	87,182
Revolving loans amortized cost basis	390,190
Revolving loans converted to term	7,642
Total Loans	1,115,985
Consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	660
2017	164
2016	0
Prior	(161)
Revolving loans amortized cost basis	1,235
Revolving loans converted to term	403
Total Loans	$ 2,301