Note 10 - Financial Instrument Commitments (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Standby letters of credit	$ 17,655
Maximum [Member]
Commitments And Contingencies Disclosure [Line Items]
Standby letters of credit expiration period	1 year