BANK PREMISES AND EQUIPMENT (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total cost	$ 218,921,000	$ 182,787,000
Accumulated depreciation	(95,247,000)	(85,206,000)
Net bank premises and equipment	123,674,000	97,581,000
Depreciation expense	11,400,000	9,100,000	$ 8,500,000
Rental Income, Nonoperating	1,600,000	1,600,000	1,300,000
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	1,300,000	1,300,000	$ 939,000
Land [Member]
Property, Plant and Equipment [Line Items]
Total cost	32,619,000	24,502,000
Bank Premises [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 62,455,000	53,052,000
Bank Premises [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Bank Premises [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 35,498,000	27,615,000
Leasehold Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	1 year
Leasehold Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	27 years
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 77,705,000	66,974,000
Furniture and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Furniture and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	12 years
Equipment Leased to Other Party [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 10,644,000	$ 10,644,000
Equipment Leased to Other Party [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years