BANK PREMISES AND EQUIPMENT (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total cost	$ 182,787,000	$ 171,227,000
Accumulated depreciation	(85,206,000)	(76,505,000)
Net bank premises and equipment	97,581,000	94,722,000
Depreciation expense	9,100,000	8,500,000	$ 7,300,000
Rental Income, Nonoperating	1,600,000	1,300,000
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	1,300,000	939,000
Land [Member]
Property, Plant and Equipment [Line Items]
Total cost	24,502,000	23,719,000
Bank Premises [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 53,052,000	49,159,000
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	$ 27,615,000	25,184,000
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	$ 66,974,000	62,521,000
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