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