Note 3 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Impaired Financing Receivable, Interest Income, Accrual Method	$ 300,000	$ 300,000	$ 800,000	$ 1,000,000
Loans and Leases Receivable Nonaccrual Loans Interest Income Recognized	0	$ 0	0	$ 0
Loans and Leases Receivable, Net of Deferred Income	2,406,377,000		2,406,377,000		$ 2,277,727,000
Loans and Leases Receivable Period Increase (Decrease)			$ 129,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)			5.60%
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	16,500,000		$ 16,500,000		24,600,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	$ 7,000,000		$ 7,000,000		$ 13,100,000
Minimum Number of Days Past Due at Period End For Loans Modified as Troubled Debt Restructurings			30 days