Note 8 - Shareholders' Equity - Information About Stock Options Granted (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares shares
Options outstanding, range of exercise price, lower range (in dollars per share)	$ 40
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 70
Options outstanding, number outstanding (in shares) | shares	793
Options outstanding, aggregate intrinsic value | $	$ 755
Options outstanding, weighted average remaining contractual life (Year)	7 years 1 month 6 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 60
Options exercisable, number outstanding (in shares) | shares	446
Options exercisable, aggregate intrinsic value | $	$ 640
Options exercisable, weighted average remaining contractual life (Year)	6 years 1 month 6 days
$40 - 45 (in dollars per share)	$ 60
Range 1 [Member]
Options outstanding, range of exercise price, lower range (in dollars per share)	40
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 45
Options outstanding, number outstanding (in shares) | shares	34
Options outstanding, aggregate intrinsic value | $	$ 527
Options outstanding, weighted average remaining contractual life (Year)	3 years 9 months 18 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 42
Options exercisable, number outstanding (in shares) | shares	34
Options exercisable, aggregate intrinsic value | $	$ 527
Options exercisable, weighted average remaining contractual life (Year)	3 years 9 months 18 days
$40 - 45 (in dollars per share)	$ 42
Range 2 [Member]
Options outstanding, range of exercise price, lower range (in dollars per share)	45
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 50
Options outstanding, number outstanding (in shares) | shares	0
Options outstanding, aggregate intrinsic value | $	$ 0
Options outstanding, weighted average exercise price (in dollars per share)	$ 0
Options exercisable, number outstanding (in shares) | shares	0
Options exercisable, aggregate intrinsic value | $	$ 0
$40 - 45 (in dollars per share)	$ 0
Range 3 [Member]
Options outstanding, range of exercise price, lower range (in dollars per share)	50
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 55
Options outstanding, number outstanding (in shares) | shares	15
Options outstanding, aggregate intrinsic value | $	$ 67
Options outstanding, weighted average remaining contractual life (Year)	2 years 1 month 6 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 53
Options exercisable, number outstanding (in shares) | shares	15
Options exercisable, aggregate intrinsic value | $	$ 67
Options exercisable, weighted average remaining contractual life (Year)	2 years 1 month 6 days
$40 - 45 (in dollars per share)	$ 53
Range 4 [Member]
Options outstanding, range of exercise price, lower range (in dollars per share)	55
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 60
Options outstanding, number outstanding (in shares) | shares	260
Options outstanding, aggregate intrinsic value | $	$ 161
Options outstanding, weighted average remaining contractual life (Year)	7 years 9 months 18 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 57
Options exercisable, number outstanding (in shares) | shares	83
Options exercisable, aggregate intrinsic value | $	$ 46
Options exercisable, weighted average remaining contractual life (Year)	5 years 1 month 6 days
$40 - 45 (in dollars per share)	$ 57
Range 5 [Member]
Options outstanding, range of exercise price, lower range (in dollars per share)	60
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 65
Options outstanding, number outstanding (in shares) | shares	316
Options outstanding, weighted average remaining contractual life (Year)	6 years 7 months 6 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 62
Options exercisable, number outstanding (in shares) | shares	258
Options exercisable, weighted average remaining contractual life (Year)	6 years 6 months
$40 - 45 (in dollars per share)	$ 62
Range 6 [Member]
Options outstanding, range of exercise price, lower range (in dollars per share)	65
Options outstanding, range of exercise price, upper range (in dollars per share)	$ 70
Options outstanding, number outstanding (in shares) | shares	168
Options outstanding, aggregate intrinsic value | $	$ 0
Options outstanding, weighted average remaining contractual life (Year)	8 years 1 month 6 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 66
Options exercisable, number outstanding (in shares) | shares	56
Options exercisable, aggregate intrinsic value | $	$ 0
Options exercisable, weighted average remaining contractual life (Year)	8 years
$40 - 45 (in dollars per share)	$ 66