FAIR VALUE - Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis - (Details) - Non-recurring basis - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Assets:
Impaired servicing rights	$ 1,083	$ 531
Total impaired loans	2,537	1,140
Recorded investment of impaired loans	4,008	2,393
Valuation allowance of impaired loans	1,471	1,253
Additional provision for loan losses	1,158	769
Gross outstanding balance of servicing rights	1,283	731
Valuation allowance of servicing rights	200	200
Servicing right recovery included in earnings		200
Commercial and industrial
Assets:
Total impaired loans	260
Recorded investment of impaired loans	689
Valuation allowance of impaired loans	429
Agricultural
Assets:
Total impaired loans	972
Recorded investment of impaired loans	1,441
Valuation allowance of impaired loans	469
Farm
Assets:
Total impaired loans	745
Recorded investment of impaired loans	1,105
Valuation allowance of impaired loans	360
1-4 family
Assets:
Total impaired loans		1,082
Other
Assets:
Total impaired loans	560	58
Recorded investment of impaired loans	773
Valuation allowance of impaired loans	213
Significant Unobservable Inputs (Level 3)
Assets:
Impaired servicing rights	1,083	531
Total impaired loans	2,537	1,140
Significant Unobservable Inputs (Level 3) | Commercial and industrial
Assets:
Total impaired loans	260
Significant Unobservable Inputs (Level 3) | Agricultural
Assets:
Total impaired loans	972
Significant Unobservable Inputs (Level 3) | Farm
Assets:
Total impaired loans	745
Significant Unobservable Inputs (Level 3) | 1-4 family
Assets:
Total impaired loans		1,082
Significant Unobservable Inputs (Level 3) | Other
Assets:
Total impaired loans	$ 560	$ 58