Note 3 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Loans and Leases Receivable, Net of Deferred Income	$ 2,554,272,000		$ 2,554,272,000		$ 2,378,620,000
Loans and Leases Receivable Period Increase (Decrease)			$ 176,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)			7.40%
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	12,400,000		$ 12,400,000		15,500,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	5,300,000		5,300,000		$ 6,200,000
Impaired Financing Receivable, Interest Income, Accrual Method	100,000	$ 300,000	400,000	$ 800,000
Loans and Leases Receivable Nonaccrual Loans Interest Income Recognized	0	0	0	0
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 100,000	$ 100,000	$ 200,000	$ 400,000
Minimum Number of Days Past Due at Period End For Loans Modified as Troubled Debt Restructurings			30 days