Note 5 - Share-based Compensation - Performance Share Units (Details) - Performance Shares [Member]	12 Months Ended
	Dec. 31, 2025 $ / shares shares
Number of shares unvested at beginning of period (in shares) | shares	352,291
Number of shares unvested at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 179.14
Number of shares granted (in shares) | shares	104,360
Number of shares granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 164.79
Number of shares vested (in shares) | shares	(84,001)
Number of shares vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 172.53
Number of shares forfeited (in shares) | shares	(35,124)
Number of shares forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 188.22
Number of shares unvested at end of period (in shares) | shares	337,526
Number of shares unvested at end of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 175.4