Note 10 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for loan losses	$ 2,058	$ 3,285
Deferred compensation	135	236
Postretirement benefit obligations	3,605	5,825
Other real estate owned	621	1,303
Self-funded insurance	114	232
Paid time off	472	815
Depreciation	1,059	1,630
Intangibles	806	1,878
Unrealized loss on available for sale investment securities, net	933	1,811
Other	147	239
Total deferred tax assets	9,950	17,254
Prepaid expenses		153
Federal Home Loan Bank stock dividends	621	1,035
Deferred loan fees	523	846
Other	31	52
Total deferred tax liabilities	1,175	2,086
Net deferred tax asset	$ 8,775	$ 15,168