FAIR VALUE - Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Assets:
Change occurred in the valuation allowance		$ 50		$ 50
Non-recurring basis
Assets:
Impaired servicing rights	$ 974		$ 974		$ 1,083
Total impaired loans	5,018		5,018		2,537
Recorded investment of impaired loans	6,980		6,980		4,008
Valuation allowance of impaired loans	1,962		1,962		1,471
Provision expenses of impaired loans	220	$ 354	885	$ 406
Gross outstanding balance of servicing rights	11		11		1,283
Valuation allowance of servicing rights			200		200
Non-recurring basis | Commercial and industrial
Assets:
Total impaired loans	74		74		260
Recorded investment of impaired loans	142		142
Valuation allowance of impaired loans	68		68
Non-recurring basis | Agricultural
Assets:
Total impaired loans	787		787		972
Recorded investment of impaired loans	1,488		1,488
Valuation allowance of impaired loans	701		701
Non-recurring basis | Hotel
Assets:
Total impaired loans	2,749		2,749
Recorded investment of impaired loans	2,950		2,950
Valuation allowance of impaired loans	201		201
Non-recurring basis | Farm
Assets:
Total impaired loans	795		795		745
Recorded investment of impaired loans	1,345		1,345
Valuation allowance of impaired loans	550		550
Non-recurring basis | Other
Assets:
Total impaired loans	613		613		560
Non-recurring basis | Other real estate
Assets:
Total impaired loans	613		613
Recorded investment of impaired loans	1,055		1,055
Valuation allowance of impaired loans	442		442
Non-recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Impaired servicing rights	974		974		1,083
Total impaired loans	5,018		5,018		2,537
Non-recurring basis | Significant Unobservable Inputs (Level 3) | Commercial and industrial
Assets:
Total impaired loans	74		74		260
Non-recurring basis | Significant Unobservable Inputs (Level 3) | Agricultural
Assets:
Total impaired loans	787		787		972
Non-recurring basis | Significant Unobservable Inputs (Level 3) | Hotel
Assets:
Total impaired loans	2,749		2,749
Non-recurring basis | Significant Unobservable Inputs (Level 3) | Farm
Assets:
Total impaired loans	795		795		745
Non-recurring basis | Significant Unobservable Inputs (Level 3) | Other
Assets:
Total impaired loans	$ 613		$ 613		$ 560