Note 11 - Securities Sold Under Agreement to Repurchase - Securities Sold Under Agreements to Repurchase by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Securities sold under agreement to repurchase	$ 13,445	$ 19,114
US Treasuries and Government Agencies [Member]
Securities sold under agreement to repurchase	82	3,318
Residential Mortgage-backed Securities [Member]
Securities sold under agreement to repurchase	13,363	15,796
Maturity Overnight and Continuous [Member]
Securities sold under agreement to repurchase	13,445	19,114
Maturity Overnight and Continuous [Member] | US Treasuries and Government Agencies [Member]
Securities sold under agreement to repurchase	82	3,318
Maturity Overnight and Continuous [Member] | Residential Mortgage-backed Securities [Member]
Securities sold under agreement to repurchase	13,363	15,796
Maturity Less than 30 Days [Member]
Securities sold under agreement to repurchase	0	0
Maturity Less than 30 Days [Member] | US Treasuries and Government Agencies [Member]
Securities sold under agreement to repurchase		0
Maturity Less than 30 Days [Member] | Residential Mortgage-backed Securities [Member]
Securities sold under agreement to repurchase	0	0
Maturity 30 to 90 Days [Member]
Securities sold under agreement to repurchase	0	0
Maturity 30 to 90 Days [Member] | US Treasuries and Government Agencies [Member]
Securities sold under agreement to repurchase		0
Maturity 30 to 90 Days [Member] | Residential Mortgage-backed Securities [Member]
Securities sold under agreement to repurchase	0	0
Maturity Greater than 90 Days [Member]
Securities sold under agreement to repurchase	0	0
Maturity Greater than 90 Days [Member] | US Treasuries and Government Agencies [Member]
Securities sold under agreement to repurchase		0
Maturity Greater than 90 Days [Member] | Residential Mortgage-backed Securities [Member]
Securities sold under agreement to repurchase	$ 0	$ 0