Note 11 - Equity Incentive Plan - Performance Stock Units (Details) - Performance Shares [Member]	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Outstanding, shares (in shares) | shares	178,297
Outstanding, weighted average grant date fair value (in dollars per share) | $ / shares	$ 35.93
Granted, shares (in shares) | shares	0
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0
Vested, shares (in shares) | shares	0
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0
Forfeited and cancelled, shares (in shares) | shares	(18,500)
Forfeited and cancelled, weighted average grant date fair value (in dollars per share) | $ / shares	$ 37.02
Outstanding, shares (in shares) | shares	159,797
Outstanding, weighted average grant date fair value (in dollars per share) | $ / shares	$ 35.80