Note 13 - Stock-based Compensation - Information about Stock Options Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Options outstanding, vested and expected to vest, number outstanding (in shares)	263,992	233,384	229,531	276,266
Options outstanding, vested and expected to vest, weighted average exercise price (in dollars per share)	$ 79.07	$ 97.78	$ 86.46	$ 72.38
Exercise Price Range One [Member]
Range of exercise prices, lower limit (in dollars per share)	$ 39.11
Options outstanding, vested and expected to vest, number outstanding (in shares)	137,829
Range of exercise prices, upper limit (in dollars per share)	$ 66.87
Options outstanding, vested and expected to vest, weighted average remaining contractual life (Year)	7 years 7 months 17 days
Options outstanding, vested and expected to vest, weighted average exercise price (in dollars per share)	$ 49.84
Options exercisable, number exercisable (in shares)	32,808
Options exercisable, weighted average exercise price (in dollars per share)	$ 56.53
Exercise Price Range Two [Member]
Range of exercise prices, lower limit (in dollars per share)	$ 66.88
Options outstanding, vested and expected to vest, number outstanding (in shares)	37,608
Range of exercise prices, upper limit (in dollars per share)	$ 96.20
Options outstanding, vested and expected to vest, weighted average remaining contractual life (Year)	6 years 8 months 19 days
Options outstanding, vested and expected to vest, weighted average exercise price (in dollars per share)	$ 89.37
Options exercisable, number exercisable (in shares)	17,016
Options exercisable, weighted average exercise price (in dollars per share)	$ 82.08
Exercise Price Range Three [Member]
Range of exercise prices, lower limit (in dollars per share)	$ 96.21
Options outstanding, vested and expected to vest, number outstanding (in shares)	88,555
Range of exercise prices, upper limit (in dollars per share)	$ 180.46
Options outstanding, vested and expected to vest, weighted average remaining contractual life (Year)	6 years 9 months 21 days
Options outstanding, vested and expected to vest, weighted average exercise price (in dollars per share)	$ 120.17
Options exercisable, number exercisable (in shares)	52,868
Options exercisable, weighted average exercise price (in dollars per share)	$ 113.74