Note 9 - Securities Sold Under Agreements to Repurchase - Securities Sold Under Agreement to Repurchase (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Securities sold under agreements to repurchase	$ 131,710,000	$ 154,771,000
Weighted average interest rate at year-end	0.16%	0.11%
Average daily balance during the year	$ 149,079,000	$ 146,826,000
Weighted average interest rate during the year	0.14%	0.11%
Maximum daily balance during the year	$ 175,088,000	$ 168,211,000