Note 10 - Securities Sold Under Agreements to Repurchase - Contractual Maturity of the Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	$ 121,400	$ 102,400
US Government Agencies Debt Securities [Member]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	121,352	102,404
Maturity Overnight [Member] | US Government Agencies Debt Securities [Member]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement	121,352	101,647
Maturity Less than 30 Days [Member] | US Government Agencies Debt Securities [Member]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement
Maturity 30 to 90 Days [Member] | US Government Agencies Debt Securities [Member]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement
Maturity Greater than 90 Days [Member] | US Government Agencies Debt Securities [Member]
Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement		$ 757