Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2018
Summary of Significant Accounting Policies [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 42,509,000	$ 32,573,000	$ 47,960,000
Trading Securities		3,596,000
Restricted Investments	1,501,000	1,017,000
Other Postretirement Benefit Expense	23,000	94,000	69,000
Allocated Share-based Compensation Expense	102,000	88,000	85,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 0	$ 0	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$ 3.88	$ 3.79	$ 4.38
Unrecognized Tax Benefits	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 0
Tax years subject to examination by tax authorities	2014
ASU 2016-01 [Member]
Summary of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	$ 645,000
ASU 2018-02 [Member]
Summary of Significant Accounting Policies [Line Items]
Reclassification from accumulated other comprehensive loss to retained earnings	805,000
Subsequent Event [Member] | ASU 2016-01 [Member]
Summary of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle on reclassification net loss from accumulated other comprehensive loss to retained earnings					$ 254,000
Other Assets [Member]
Summary of Significant Accounting Policies [Line Items]
Other Real Estate, Foreclosed Assets, and Repossessed Assets	0	$ 0
Investment in Federal Home Loan Bank Stock [Member]
Summary of Significant Accounting Policies [Line Items]
Restricted Investments	1,489,000
Investment in Atlantic Community Bankers Bank Stock [Member]
Summary of Significant Accounting Policies [Line Items]
Restricted Investments	$ 12,000
Brokerage Account [Member]
Summary of Significant Accounting Policies [Line Items]
Cash, Cash Equivalents, and Short-term Investments		1,499,000
US States and Political Subdivisions Debt Securities [Member]
Summary of Significant Accounting Policies [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds				$ 5,000,000
Trading Securities		$ 3,596,000