BANK PREMISES AND EQUIPMENT (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total cost	$ 146,762,000	$ 138,115,000
Accumulated depreciation	(68,282,000)	(62,452,000)
Net bank premises and equipment	78,480,000	75,663,000
Depreciation expense	7,300,000	7,000,000	$ 6,600,000
Impairment of Long-Lived Assets to be Disposed of	16,000	109,000	$ 670,000
Land [Member]
Property, Plant and Equipment [Line Items]
Total cost	20,585,000	20,780,000
Bank Premises [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 43,553,000	39,182,000
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	39 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 24,387,000	22,817,000
Leasehold Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	4 years
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	$ 58,237,000	$ 55,336,000
Furniture and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	1 year
Furniture and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	12 years