Note 10 - Commitments and Contingencies (Details Textual) - USD ($)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Commitments And Contingencies Disclosure [Line Items]
Standby letters of credit	$ 18,556,000
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 1,086,000	$ 2,407,000
Maximum [Member]
Commitments And Contingencies Disclosure [Line Items]
Standby letters of credit expiration period	1 year
Lessee leasing arrangements, operating leases, renewal term	10 years
Minimum [Member]
Commitments And Contingencies Disclosure [Line Items]
Lessee leasing arrangements, operating leases, renewal term	5 years