Note 10 - Share-based Compensation - Shares Authorized, Available for Future Grant and Outstanding Under Each Plan (Details)	Sep. 30, 2020 shares
Authorized (in shares)	1,650,000
Available (in shares)	1,108,491
Outstanding (in shares)	435,988
The 2016 Plan [Member]
Authorized (in shares)	1,300,000
Available (in shares)	1,065,358
Outstanding (in shares)	176,688
2014 Directors Plan [Member]
Authorized (in shares)	350,000
Available (in shares)	43,133
Outstanding (in shares)	12,000
The 2005 Plan [Member]
Authorized (in shares)
Available (in shares)	0
Outstanding (in shares)	235,300
The 2004 Directors Plan [Member]
Authorized (in shares)
Available (in shares)	0
Outstanding (in shares)	12,000