LOANS AND LEASES - Commercial and Consumer Credit Exposure by Risk Attribute (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 9,307,819	$ 9,201,665
Financing Receivable, Originated in Current Fiscal Year	383,709
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,328,197
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,609,712
Financing Receivable, Originated Three Years before Latest Fiscal Year	1,196,029
Financing Receivable, Originated Four Years before Latest Fiscal Year	924,268
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,451,089
Financing Receivable, before Allowance for Credit Loss	7,893,004
Loans and Leases Receivable, Gross		9,133,001
Financing Receivable, Revolving	1,414,815
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		2,465,877
Commercial \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		2,324,021
Commercial \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		100,954
Commercial \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		40,902
Commercial \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Construction real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		493,182
Construction real estate \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		493,182
Construction real estate \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Construction real estate \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Construction real estate \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		4,194,651
Commercial Real Estate \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		4,108,752
Commercial Real Estate \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		59,383
Commercial Real Estate \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		26,516
Commercial Real Estate \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		88,364
Lease financing \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		85,262
Lease financing \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		488
Lease financing \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		2,614
Lease financing \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Commercial segment
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		7,242,074
Commercial segment \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		7,011,217
Commercial segment \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		160,825
Commercial segment \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		70,032
Commercial segment \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		0
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		1,055,949
Residential real estate \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		1,040,787
Residential real estate \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		15,162
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		771,869
Home equity \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		766,169
Home equity \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		5,700
Installment
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		82,589
Installment \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		82,385
Installment \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		204
Credit card
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		49,184
Credit card \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		48,983
Credit card \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		201
Total consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		1,959,591
Total consumer \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		1,938,324
Total consumer \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income		21,267
Commercial segment
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,477,773	2,465,877
Financing Receivable, Originated in Current Fiscal Year	112,479
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	549,667
Financing Receivable, Originated Two Years before Latest Fiscal Year	486,808
Financing Receivable, Originated Three Years before Latest Fiscal Year	330,738
Financing Receivable, Originated Four Years before Latest Fiscal Year	207,225
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	172,347
Financing Receivable, before Allowance for Credit Loss	1,859,264
Loans and Leases Receivable, Gross		2,462,796
Financing Receivable, Revolving	618,509
Commercial segment \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,357,756
Financing Receivable, Originated in Current Fiscal Year	112,198
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	541,313
Financing Receivable, Originated Two Years before Latest Fiscal Year	463,439
Financing Receivable, Originated Three Years before Latest Fiscal Year	296,040
Financing Receivable, Originated Four Years before Latest Fiscal Year	195,719
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	166,485
Financing Receivable, before Allowance for Credit Loss	1,775,194
Financing Receivable, Revolving	582,562
Commercial segment \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	60,723
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	7,524
Financing Receivable, Originated Two Years before Latest Fiscal Year	11,814
Financing Receivable, Originated Three Years before Latest Fiscal Year	8,206
Financing Receivable, Originated Four Years before Latest Fiscal Year	3,057
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,835
Financing Receivable, before Allowance for Credit Loss	34,436
Financing Receivable, Revolving	26,287
Commercial segment \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	59,294
Financing Receivable, Originated in Current Fiscal Year	281
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	830
Financing Receivable, Originated Two Years before Latest Fiscal Year	11,555
Financing Receivable, Originated Three Years before Latest Fiscal Year	26,492
Financing Receivable, Originated Four Years before Latest Fiscal Year	8,449
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,027
Financing Receivable, before Allowance for Credit Loss	49,634
Financing Receivable, Revolving	9,660
Commercial segment \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	82,602	88,364
Financing Receivable, Originated in Current Fiscal Year	2,422
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	30,362
Financing Receivable, Originated Two Years before Latest Fiscal Year	16,619
Financing Receivable, Originated Three Years before Latest Fiscal Year	12,739
Financing Receivable, Originated Four Years before Latest Fiscal Year	9,062
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	11,398
Financing Receivable, before Allowance for Credit Loss	82,602
Loans and Leases Receivable, Gross		88,364
Financing Receivable, Revolving	0
Lease financing \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	80,354
Financing Receivable, Originated in Current Fiscal Year	2,422
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	30,362
Financing Receivable, Originated Two Years before Latest Fiscal Year	15,240
Financing Receivable, Originated Three Years before Latest Fiscal Year	12,482
Financing Receivable, Originated Four Years before Latest Fiscal Year	8,474
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	11,374
Financing Receivable, before Allowance for Credit Loss	80,354
Financing Receivable, Revolving	0
Lease financing \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	6
Financing Receivable, before Allowance for Credit Loss	6
Financing Receivable, Revolving	0
Lease financing \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,242
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,379
Financing Receivable, Originated Three Years before Latest Fiscal Year	257
Financing Receivable, Originated Four Years before Latest Fiscal Year	588
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	18
Financing Receivable, before Allowance for Credit Loss	2,242
Financing Receivable, Revolving	0
Lease financing \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Construction real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	500,311	493,182
Financing Receivable, Originated in Current Fiscal Year	4,582
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	127,531
Financing Receivable, Originated Two Years before Latest Fiscal Year	164,885
Financing Receivable, Originated Three Years before Latest Fiscal Year	79,198
Financing Receivable, Originated Four Years before Latest Fiscal Year	52,550
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	56,575
Financing Receivable, before Allowance for Credit Loss	485,321
Loans and Leases Receivable, Gross		493,167
Financing Receivable, Revolving	14,990
Construction real estate \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	500,311
Financing Receivable, Originated in Current Fiscal Year	4,582
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	127,531
Financing Receivable, Originated Two Years before Latest Fiscal Year	164,885
Financing Receivable, Originated Three Years before Latest Fiscal Year	79,198
Financing Receivable, Originated Four Years before Latest Fiscal Year	52,550
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	56,575
Financing Receivable, before Allowance for Credit Loss	485,321
Financing Receivable, Revolving	14,990
Construction real estate \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Construction real estate \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Construction real estate \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Commercial real estate - investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,180,037
Financing Receivable, Originated in Current Fiscal Year	122,395
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1,057,251
Financing Receivable, Originated Two Years before Latest Fiscal Year	493,098
Financing Receivable, Originated Three Years before Latest Fiscal Year	480,363
Financing Receivable, Originated Four Years before Latest Fiscal Year	376,429
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	585,824
Financing Receivable, before Allowance for Credit Loss	3,115,360
Financing Receivable, Revolving	64,677
Commercial real estate - investor \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	3,115,235
Financing Receivable, Originated in Current Fiscal Year	121,429
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1,052,858
Financing Receivable, Originated Two Years before Latest Fiscal Year	485,310
Financing Receivable, Originated Three Years before Latest Fiscal Year	455,332
Financing Receivable, Originated Four Years before Latest Fiscal Year	357,074
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	578,729
Financing Receivable, before Allowance for Credit Loss	3,050,732
Financing Receivable, Revolving	64,503
Commercial real estate - investor \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	43,541
Financing Receivable, Originated in Current Fiscal Year	966
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	59
Financing Receivable, Originated Two Years before Latest Fiscal Year	957
Financing Receivable, Originated Three Years before Latest Fiscal Year	18,881
Financing Receivable, Originated Four Years before Latest Fiscal Year	19,243
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,261
Financing Receivable, before Allowance for Credit Loss	43,367
Financing Receivable, Revolving	174
Commercial real estate - investor \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	21,261
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	4,334
Financing Receivable, Originated Two Years before Latest Fiscal Year	6,831
Financing Receivable, Originated Three Years before Latest Fiscal Year	6,150
Financing Receivable, Originated Four Years before Latest Fiscal Year	112
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,834
Financing Receivable, before Allowance for Credit Loss	21,261
Financing Receivable, Revolving	0
Commercial real estate - investor \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Commercial real estate-owner
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,098,220
Financing Receivable, Originated in Current Fiscal Year	64,121
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	191,615
Financing Receivable, Originated Two Years before Latest Fiscal Year	184,381
Financing Receivable, Originated Three Years before Latest Fiscal Year	167,210
Financing Receivable, Originated Four Years before Latest Fiscal Year	177,387
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	280,683
Financing Receivable, before Allowance for Credit Loss	1,065,397
Financing Receivable, Revolving	32,823
Commercial real estate-owner \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,059,073
Financing Receivable, Originated in Current Fiscal Year	64,121
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	188,827
Financing Receivable, Originated Two Years before Latest Fiscal Year	178,010
Financing Receivable, Originated Three Years before Latest Fiscal Year	162,309
Financing Receivable, Originated Four Years before Latest Fiscal Year	173,052
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	260,262
Financing Receivable, before Allowance for Credit Loss	1,026,581
Financing Receivable, Revolving	32,492
Commercial real estate-owner \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	24,433
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	696
Financing Receivable, Originated Two Years before Latest Fiscal Year	4,112
Financing Receivable, Originated Three Years before Latest Fiscal Year	289
Financing Receivable, Originated Four Years before Latest Fiscal Year	2,549
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	16,456
Financing Receivable, before Allowance for Credit Loss	24,102
Financing Receivable, Revolving	331
Commercial real estate-owner \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	14,714
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,092
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,259
Financing Receivable, Originated Three Years before Latest Fiscal Year	4,612
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,786
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,965
Financing Receivable, before Allowance for Credit Loss	14,714
Financing Receivable, Revolving	0
Commercial real estate-owner \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	0
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, before Allowance for Credit Loss	0
Financing Receivable, Revolving	0
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,061,792	1,055,949
Financing Receivable, Originated in Current Fiscal Year	61,423
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	320,217
Financing Receivable, Originated Two Years before Latest Fiscal Year	168,463
Financing Receivable, Originated Three Years before Latest Fiscal Year	96,575
Financing Receivable, Originated Four Years before Latest Fiscal Year	83,603
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	331,511
Financing Receivable, before Allowance for Credit Loss	1,061,792
Loans and Leases Receivable, Gross		1,029,129
Financing Receivable, Revolving	0
Residential real estate \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	1,054,812
Financing Receivable, Originated in Current Fiscal Year	61,423
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	319,956
Financing Receivable, Originated Two Years before Latest Fiscal Year	168,242
Financing Receivable, Originated Three Years before Latest Fiscal Year	95,898
Financing Receivable, Originated Four Years before Latest Fiscal Year	83,240
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	326,053
Financing Receivable, before Allowance for Credit Loss	1,054,812
Financing Receivable, Revolving	0
Residential real estate \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	6,980
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	261
Financing Receivable, Originated Two Years before Latest Fiscal Year	221
Financing Receivable, Originated Three Years before Latest Fiscal Year	677
Financing Receivable, Originated Four Years before Latest Fiscal Year	363
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	5,458
Financing Receivable, before Allowance for Credit Loss	6,980
Financing Receivable, Revolving	0
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	781,243	771,869
Financing Receivable, Originated in Current Fiscal Year	9,019
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	27,373
Financing Receivable, Originated Two Years before Latest Fiscal Year	23,925
Financing Receivable, Originated Three Years before Latest Fiscal Year	15,105
Financing Receivable, Originated Four Years before Latest Fiscal Year	13,734
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	62,552
Financing Receivable, before Allowance for Credit Loss	151,708
Loans and Leases Receivable, Gross		769,271
Financing Receivable, Revolving	629,535
Home equity \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	776,545
Financing Receivable, Originated in Current Fiscal Year	9,019
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	27,294
Financing Receivable, Originated Two Years before Latest Fiscal Year	23,829
Financing Receivable, Originated Three Years before Latest Fiscal Year	15,066
Financing Receivable, Originated Four Years before Latest Fiscal Year	13,639
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	62,117
Financing Receivable, before Allowance for Credit Loss	150,964
Financing Receivable, Revolving	625,581
Home equity \| Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	4,698
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	79
Financing Receivable, Originated Two Years before Latest Fiscal Year	96
Financing Receivable, Originated Three Years before Latest Fiscal Year	39
Financing Receivable, Originated Four Years before Latest Fiscal Year	95
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	435
Financing Receivable, before Allowance for Credit Loss	744
Financing Receivable, Revolving	3,954
Total consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	80,085	82,589
Financing Receivable, Originated in Current Fiscal Year	7,267
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	24,181
Financing Receivable, Originated Two Years before Latest Fiscal Year	17,271
Financing Receivable, Originated Three Years before Latest Fiscal Year	14,102
Financing Receivable, Originated Four Years before Latest Fiscal Year	4,275
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,465
Financing Receivable, before Allowance for Credit Loss	71,561
Loans and Leases Receivable, Gross		82,331
Financing Receivable, Revolving	8,524
Total consumer \| Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Net of Deferred Income	79,894
Financing Receivable, Originated in Current Fiscal Year	7,267
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	24,153
Financing Receivable, Originated Two Years before Latest Fiscal Year	17,227
Financing Receivable, Originated Three Years before Latest Fiscal Year	14,093
Financing Receivable, Originated Four Years before Latest Fiscal Year	4,260
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,370
Financing Receivable, before Allowance for Credit Loss	71,370
Financing Receivable, Revolving	8,524

LOANS AND LEASES - Commercial and Consumer Credit Exposure by Risk Attribute (Details) - USD ($)
$ in Thousands

Mar. 31, 2020

Dec. 31, 2019

Financing Receivable, Credit Quality Indicator [Line Items]

Loans and Leases Receivable, Net of Deferred Income

$ 9,307,819

$ 9,201,665

Financing Receivable, Originated in Current Fiscal Year

383,709

Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year

2,328,197

Financing Receivable, Originated Two Years before Latest Fiscal Year