Note 13 - Stock-based Compensation - Restricted Stock Options (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restricted stock (in shares)	343,782	307,199	314,973
Restricted stock, weighted-average grant date fair value (in dollars per share)	$ 111.79	$ 98.87	$ 89.55
Granted (in shares)	315,432	205,996	108,179
Granted, weighted-average grant date fair value (in dollars per share)	$ 42.03	$ 123.61	$ 111.76
Restrictions lapsed (in shares)	(130,452)	(115,908)	(101,941)
Restrictions lapsed, weighted-average grant date fair value (in dollars per share)	$ 101.32	$ 91.26	$ 84.70
Forfeited (in shares)	(50,166)	(53,505)	(14,012)
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 96.48	$ 128.05	$ 94.24
Restricted stock (in shares)	478,596	343,782	307,199
Restricted stock, weighted-average grant date fair value (in dollars per share)	$ 70.36	$ 111.79	$ 98.87