Note 15 - Fair Value Measurements and Fair Values of Financial Instruments (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Servicing Fees	$ 1,800,000	$ 1,800,000	$ 1,700,000
Servicing Asset	204,900,000	191,000,000
Interest and Fee Income, Loans Held-for-sale, Mortgages	976,000
Loans Held-for-sale, Write-down	0	0
Mortgages Held-for-sale, Fair Value Disclosure	43,375,000	23,911,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Mortgages Held-for-sale, Fair Value Disclosure	$ 0	0
SBA Servicing Assets [Member]
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 10 Percent Adverse Change in Key Assumptions, Percent	10.00%
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 20 Percent Adverse Change in Key Assumptions	20.00%
Interest and Fees [Member]
Interest and Fee Income, Loans Held-for-sale, Mortgages		$ 283,000