Note 3 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Loans and Leases Receivable Nonaccrual Loans Interest Income Recognized			$ 0	$ 0
Loans and Leases Receivable, Net of Deferred Income	$ 2,379,940,000		2,379,940,000		$ 2,277,727,000
Loans and Leases Receivable Period Increase (Decrease)			$ 102,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)			4.50%
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	19,200,000		$ 19,200,000		24,600,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	8,800,000		8,800,000		$ 13,100,000
Impaired Financing Receivable, Interest Income, Accrual Method	$ 200,000	$ 400,000	$ 500,000	$ 800,000
Minimum Number of Days Past Due at Period End For Loans Modified as Troubled Debt Restructurings			30 days