Note 5 - Share-based Compensation - Restricted Share Units (Details) - Restricted Stock Units (RSUs) [Member]	12 Months Ended
	Dec. 31, 2024 $ / shares shares
Number of shares unvested at beginning of period (in shares) | shares	936,492
Number of shares unvested at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 147.02
Number of shares granted (in shares) | shares	269,322
Number of shares granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 192.98
Number of shares vested (in shares) | shares	(430,890)
Number of shares vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 146.06
Number of shares forfeited (in shares) | shares	(37,687)
Number of shares forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 171.81
Number of shares unvested at end of period (in shares) | shares	737,237
Number of shares unvested at end of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 163.83