Note 8 - Stock-based Compensation and Expense - Changes to Non-vested Restricted Stock Units (Details)	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Non-vested shares, balance (in shares) | shares	104,094
Non-vested shares, fair value price per share (in dollars per share) | $ / shares	$ 55.35
Forfeited (in shares) | shares	(2,147)
Forfeited (in dollars per share) | $ / shares	$ 106.08
Restricted Stock Units (RSUs) [Member]
Granted (in shares) | shares	0
Granted, fair value price per share (in dollars per share) | $ / shares	$ 0
Vested (in shares) | shares	(14,802)
Vested, fair value price per share (in dollars per share) | $ / shares	$ 78.70
Non-vested shares, balance (in shares) | shares	87,145
Non-vested shares, fair value price per share (in dollars per share) | $ / shares	$ 50.13