FAIR VALUE - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)
Quantitative information about level 3 fair value measurements for financial instruments measured at fair value
Number of times a sample of prices supplied by the pricing agent is validated by comparison to prices obtained from other third party sources | item	2
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	$ 1,083,903	$ 1,007,540
Transfers between Level 1 and Level 2
Transfers of assets from Level 1 to Level 2	0		$ 0
Transfers of assets from Level 2 to Level 1	0		$ 0
U. S. government agency
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	116	955
State and municipal
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	389,126	369,286
Mortgage-backed securities-residential (Government Sponsored Entity)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	402,226	446,630
Collateralized mortgage obligations (Government Sponsored Entity)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	282,757	179,401
Equity securities
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	4,670	4,670
Other securities
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	5,008	6,598
Recurring basis | Carrying Value
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	1,083,903	1,007,540
Mortgage banking derivatives	854	648
Fair value, assets	3,666	3,003
Derivative liability	(3,666)	(3,003)
Recurring basis | Carrying Value | U. S. government agency
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	116	955
Recurring basis | Carrying Value | State and municipal
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	389,126	369,286
Recurring basis | Carrying Value | Mortgage-backed securities-residential (Government Sponsored Entity)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	402,226	446,630
Recurring basis | Carrying Value | Collateralized mortgage obligations (Government Sponsored Entity)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	282,757	179,401
Recurring basis | Carrying Value | Equity securities
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	4,670	4,670
Recurring basis | Carrying Value | Other securities
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	5,008	6,598
Recurring basis | Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	4,670	4,670
Recurring basis | Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	1,064,745	986,152
Mortgage banking derivatives	854	648
Fair value, assets	3,666	3,003
Derivative liability	(3,666)	(3,003)
Recurring basis | Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	14,488	16,718
Recurring basis | Estimated Fair Value | U. S. government agency | Significant Other Observable Inputs (Level 2)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	116	955
Recurring basis | Estimated Fair Value | State and municipal | Significant Other Observable Inputs (Level 2)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	379,646	359,166
Recurring basis | Estimated Fair Value | State and municipal | Significant Unobservable Inputs (Level 3)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	9,480	10,120
Recurring basis | Estimated Fair Value | Mortgage-backed securities-residential (Government Sponsored Entity) | Significant Other Observable Inputs (Level 2)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	402,226	446,630
Recurring basis | Estimated Fair Value | Collateralized mortgage obligations (Government Sponsored Entity) | Significant Other Observable Inputs (Level 2)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	282,757	179,401
Recurring basis | Estimated Fair Value | Equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	4,670	4,670
Recurring basis | Estimated Fair Value | Other securities | Significant Unobservable Inputs (Level 3)
Assets and Liabilities Measured on a Recurring Basis
Financial Assets	$ 5,008	$ 6,598