Note 10 - Share-based Compensation - Shares Authorized, Available for Future Grant and Outstanding Under Each Plan (Details)	Dec. 31, 2021 shares
Authorized (in shares)	1,950,000
Available (in shares)	1,280,816
Outstanding (in shares)	283,674
The 2016 Plan [Member]
Authorized (in shares)	1,300,000
Available (in shares)	993,121
Outstanding (in shares)	214,174
2014 Directors Plan [Member]
Authorized (in shares)	650,000
Available (in shares)	287,695
Outstanding (in shares)	12,000
The 2005 Plan [Member]
Authorized (in shares)	0
Available (in shares)	0
Outstanding (in shares)	51,500
The 2004 Directors Plan [Member]
Authorized (in shares)	0
Available (in shares)	0
Outstanding (in shares)	6,000