Note 5 - Share-based Compensation - Performance Share Units (Details) - Performance Shares [Member]	12 Months Ended
	Dec. 31, 2024 $ / shares shares
Number of shares unvested at beginning of period (in shares) | shares	386,723
Number of shares unvested at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 163.87
Number of shares granted (in shares) | shares	140,469
Number of shares granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 195.24
Number of shares vested (in shares) | shares	(138,115)
Number of shares vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 150.73
Number of shares forfeited (in shares) | shares	(36,786)
Number of shares forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 186.85
Number of shares unvested at end of period (in shares) | shares	352,291
Number of shares unvested at end of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 179.14