FAIR VALUE - Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis - (Details) - Non-recurring basis - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Assets:
Impaired servicing rights	$ 1,039		$ 1,083
Total impaired loans	5,507		2,537
Recorded investment of impaired loans	7,304		4,008
Valuation allowance of impaired loans	1,797		1,471
Provision expenses of impaired loans	666	$ 125
Gross outstanding balance of servicing rights	1,239		1,283
Valuation allowance of servicing rights	200		200
Commercial and industrial
Assets:
Total impaired loans	222		260
Recorded investment of impaired loans	295
Valuation allowance of impaired loans	73
Agricultural
Assets:
Total impaired loans	919		972
Recorded investment of impaired loans	1,595
Valuation allowance of impaired loans	676
Hotel
Assets:
Total impaired loans	2,782
Recorded investment of impaired loans	2,983
Valuation allowance of impaired loans	201
Farm
Assets:
Total impaired loans	843		745
Recorded investment of impaired loans	1,371
Valuation allowance of impaired loans	528
Other
Assets:
Total impaired loans	741		560
Recorded investment of impaired loans	1,060
Valuation allowance of impaired loans	319
Significant Unobservable Inputs (Level 3)
Assets:
Impaired servicing rights	1,039		1,083
Total impaired loans	5,507		2,537
Significant Unobservable Inputs (Level 3) | Commercial and industrial
Assets:
Total impaired loans	222		260
Significant Unobservable Inputs (Level 3) | Agricultural
Assets:
Total impaired loans	919		972
Significant Unobservable Inputs (Level 3) | Hotel
Assets:
Total impaired loans	2,782
Significant Unobservable Inputs (Level 3) | Farm
Assets:
Total impaired loans	843		745
Significant Unobservable Inputs (Level 3) | Other
Assets:
Total impaired loans	$ 741		$ 560