Note 9 - Fair Value Measurements and Disclosures (Details) - Financial Assets Measured at Fair Value on a Recurring and Nonrecurring Basis - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Trading Securities
Trading securities	$ 3,625,000	$ 4,207,000
Securities available-for-sale
Investment securities available-for-sale	362,568,000	375,219,000
U.S. Government agencies and sponsored enterprises (GSEs):
Recurring fair value measurements	366,193,000	379,426,000
Nonrecurring fair value measurements
Nonrecurring fair value measurements	1,038,000	3,827,000
Impaired Loans [Member]
Nonrecurring fair value measurements
Nonrecurring fair value measurements	903,000	3,715,000
Mortgage Servicing Rights [Member]
Nonrecurring fair value measurements
Nonrecurring fair value measurements	135,000	112,000
US States and Political Subdivisions Debt Securities [Member]
Trading Securities
Trading securities	3,625,000	4,207,000
Securities available-for-sale
Investment securities available-for-sale	83,042,000	72,569,000
US Government Agencies Debt Securities [Member]
Securities available-for-sale
Investment securities available-for-sale	57,490,000	62,665,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale
Investment securities available-for-sale	133,281,000	136,192,000
Collateralized Mortgage Obligations [Member]
Securities available-for-sale
Investment securities available-for-sale	73,034,000	87,662,000
Collateralized Debt Obligations [Member]
Securities available-for-sale
Investment securities available-for-sale	2,600,000	2,439,000
Corporate Debt Securities [Member]
Securities available-for-sale
Investment securities available-for-sale	6,029,000	6,037,000
Equity Securities [Member]
Securities available-for-sale
Investment securities available-for-sale	7,092,000	7,655,000
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Investment securities available-for-sale	7,092,000	7,655,000
U.S. Government agencies and sponsored enterprises (GSEs):
Recurring fair value measurements	7,092,000	7,655,000
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Securities available-for-sale
Investment securities available-for-sale	7,092,000	7,655,000
Fair Value, Inputs, Level 2 [Member]
Trading Securities
Trading securities	3,625,000	4,207,000
Securities available-for-sale
Investment securities available-for-sale	352,876,000	365,125,000
U.S. Government agencies and sponsored enterprises (GSEs):
Recurring fair value measurements	356,501,000	369,332,000
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Trading Securities
Trading securities	3,625,000	4,207,000
Securities available-for-sale
Investment securities available-for-sale	83,042,000	72,569,000
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Securities available-for-sale
Investment securities available-for-sale	57,490,000	62,665,000
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale
Investment securities available-for-sale	133,281,000	136,192,000
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Securities available-for-sale
Investment securities available-for-sale	73,034,000	87,662,000
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Securities available-for-sale
Investment securities available-for-sale	6,029,000	6,037,000
Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Investment securities available-for-sale	2,600,000	2,439,000
U.S. Government agencies and sponsored enterprises (GSEs):
Recurring fair value measurements	2,600,000	2,439,000
Nonrecurring fair value measurements
Nonrecurring fair value measurements	1,038,000	3,827,000
Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member]
Nonrecurring fair value measurements
Nonrecurring fair value measurements	903,000	3,715,000
Fair Value, Inputs, Level 3 [Member] | Mortgage Servicing Rights [Member]
Nonrecurring fair value measurements
Nonrecurring fair value measurements	135,000	112,000
Fair Value, Inputs, Level 3 [Member] | Collateralized Debt Obligations [Member]
Securities available-for-sale
Investment securities available-for-sale	$ 2,600,000	$ 2,439,000