Note 11 - Federal Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets
Allowance for loan losses	$ 4,095,000	$ 6,286,000
Deferred compensation	673,000	1,175,000
Stock compensation	501,000	786,000
Nonaccrual loan interest income	425,000	623,000
Deferred loan fees	211,000	496,000
Deferred Tax Assets, Capital Loss Carryforwards	94,000	157,000
Fair value write-downs on foreclosed properties	23,000	24,000
Fair value of interest rate swap	0	30,000
Unrealized loss on securities	1,303,000	2,976,000
Other	311,000	408,000
Deferred tax asset before valuation allowance	7,636,000	12,961,000
Valuation allowance	(94,000)	(157,000)
Deferred tax asset after valuation allowance	7,542,000	12,804,000
Deferred income tax liabilities
Depreciation	727,000	928,000
Prepaid expenses	244,000	463,000
Core deposit intangible	1,565,000	3,423,000
Mortgage loan servicing rights	1,072,000	1,940,000
Business combination adjustments	1,784,000	2,183,000
Other	146,000	199,000
Deferred tax liability	5,538,000	9,136,000
Total net deferred tax asset	$ 2,004,000	$ 3,668,000