Note 14 - Financial Instruments and Fair Value Measurements - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Cash and cash equivalents	$ 147,594	$ 126,145
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	147,594	126,145
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Restricted equity securities	4,761	4,357
Interest receivable	3,457	3,755
Interest payable	(50)	(40)
Financial liabilities:
Interest payable	(50)	(40)
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Restricted equity securities	4,761	4,357
Interest receivable	3,457	3,755
Interest payable	(50)	(40)
Financial liabilities:
Interest payable	(50)	(40)
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Loans, net	741,047	702,220
Deposits	(1,019,929)	(986,495)
Financial liabilities:
Deposits	(1,019,929)	(986,495)
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Loans, net	742,484	697,369
Deposits	(1,019,654)	(986,096)
Commitments and standby letters of credit	(1,647)	(1,539)
Financial liabilities:
Deposits	(1,019,654)	(986,096)
Off-balance-sheet assets (liabilities):
Commitments and standby letters of credit	$ (1,647)	$ (1,539)