Note 6 - Share-based Compensation - Non-vested Stock (Details) - Common Stock [Member]	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Outstanding (in shares) | shares	6,005
Outstanding (in dollars per share) | $ / shares	$ 38.30
Granted (in shares) | shares	12,698
Granted (in dollars per share) | $ / shares	$ 42.92
Forfeited (in shares) | shares	(6,005)
Forfeited (in dollars per share) | $ / shares	$ 38.30
Outstanding (in shares) | shares	12,698
Outstanding (in dollars per share) | $ / shares	$ 42.92