Note 9 - Securities Sold Under Agreements to Repurchase - Maturity of Short and Long-term Repurchase Agreements (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Short and long-term purchase agreements	$ 32,569	$ 36,370
US Government-sponsored Enterprises Debt Securities [Member]
Short and long-term purchase agreements	1,533	7,182
Residential Mortgage Backed Securities [Member]
Short and long-term purchase agreements	31,036	29,188
Maturity Overnight [Member]
Short and long-term purchase agreements	30,134	33,682
Maturity Overnight [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Short and long-term purchase agreements	0	5,596
Maturity Overnight [Member] | Residential Mortgage Backed Securities [Member]
Short and long-term purchase agreements	30,134	28,086
Maturity Less than 30 Days [Member]
Short and long-term purchase agreements	1,203	1,203
Maturity Less than 30 Days [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Short and long-term purchase agreements	501	301
Maturity Less than 30 Days [Member] | Residential Mortgage Backed Securities [Member]
Short and long-term purchase agreements	702	902
Maturity 30 to 90 Days [Member]
Short and long-term purchase agreements	200	0
Maturity 30 to 90 Days [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Short and long-term purchase agreements	0	0
Maturity 30 to 90 Days [Member] | Residential Mortgage Backed Securities [Member]
Short and long-term purchase agreements	200	0
Maturity 90 Days to One Year [Member]
Short and long-term purchase agreements	0	458
Maturity 90 Days to One Year [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Short and long-term purchase agreements	0	258
Maturity 90 Days to One Year [Member] | Residential Mortgage Backed Securities [Member]
Short and long-term purchase agreements	0	200
Maturity Over One Year to Four Years [Member]
Short and long-term purchase agreements	1,032	1,027
Maturity Over One Year to Four Years [Member] | US Government-sponsored Enterprises Debt Securities [Member]
Short and long-term purchase agreements	1,032	1,027
Maturity Over One Year to Four Years [Member] | Residential Mortgage Backed Securities [Member]
Short and long-term purchase agreements	$ 0	$ 0