ACCOUNTING POLICIES (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Component Calculation Segment Factor	Mar. 31, 2017 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of broad components used in allowance methodology | Component	2
Number of calculations used for general loan loss allocation | Calculation	2
Number of main loan segments | Segment	5
Period of historical net charge-off data for each loan class used in determining allowance level	36 months
Number of qualitative environmental factors used in qualitative calculation for loan loss allocation | Factor	8
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Salaries and employee benefits	$ 51,859	$ 42,907
Other expenses	$ 2,938	2,545
Core Deposits [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)	7 years
Core Deposits [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)	20 years
Customer Relationships [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)	7 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)	20 years
Commercial Portfolio Segment [Member] | Minimum [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Threshold balance of loans individually evaluated for impairment	$ 500
ASU 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Salaries and employee benefits		(1,500)
Other expenses		$ 1,500