v3.26.1
Note 8 - Equity Compensation Plans - Summary of Stock Activity (Details) - USD ($)
$ / shares in Units, $ in Millions
 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Outstanding beginning balance, options (in shares) 1,676,340    
Outstanding beginning balance, options, weighted average exercise price (in dollars per share) $ 180.4    
Outstanding, options, aggregate intrinsic value $ 28.0   $ 72.6
Granted, options (in shares) 293,498    
Weighted average grant price (in dollars per share) $ 220.59 $ 273.92  
Dividend reinvestment, options (in shares) 0    
Dividend reinvestment, options, weighted average exercise price (in (in dollars per share)    
Exercised or lapsed, options (in shares) (127,648)    
Exercised or lapsed, options, weighted average exercise price (in dollars per share) $ 122.9    
Exercised or lapsed, options, aggregate intrinsic value $ 9.0    
Canceled, expired or forfeited, option (in shares) (41,669)    
Canceled, expired or forfeited, options, weighted average exercise price (in dollars per share) $ 220.88    
Outstanding, option (in shares) 1,800,521    
Outstanding beginning balance, options, weighted average exercise price (in dollars per share) $ 190.09    
Exercisable, options (in shares) 1,232,127   1,178,052
Exercisable, options, weighted average exercise price (in dollars per share) $ 170.16   $ 156.76
Exercisable, options, aggregate intrinsic value $ 27.9   $ 78.8
Nonvested, options (in shares) 568,394    
Expected to vest, options (in shares) 487,811    
Restricted Stock [Member]      
Outstanding beginning balance, number of shares (in shares) 321,947    
Outstanding beginning balance, weighted average exercise price (in dollars per share) $ 242.66    
Granted, number of shares (in shares) 192,701    
Granted, weighted average exercise price (in dollars per share) $ 219.78    
Dividend reinvestment, number of shares (in shares) 0    
Dividend reinvestment (in dollars per share)    
Exercised or lapsed, number of shares (in shares) (122,754)    
Exercised or lapsed, weighted average exercise price (in dollars per share) $ 227.55    
Canceled, expired or forfeited, number of shares (in shares) (14,713)    
Canceled, expired or forfeited, weighted average exercise price (in dollars per share) $ 239.39    
Outstanding ending balance, number of shares (in shares) 377,181    
Outstanding ending balance, weighted average exercise price (in dollars per share) $ 234.32    
Nonvested, number of shares (in shares) 377,181   321,947
Expected, number of shares (in shares) 335,537    
Performance Shares [Member]      
Outstanding beginning balance, number of shares (in shares) 135,916    
Outstanding beginning balance, weighted average exercise price (in dollars per share) $ 262.39    
Granted, number of shares (in shares) 102,583    
Granted, weighted average exercise price (in dollars per share) $ 224.35    
Dividend reinvestment, number of shares (in shares) 830    
Exercised or lapsed, number of shares (in shares) (45,252)    
Exercised or lapsed, weighted average exercise price (in dollars per share) $ 204.3    
Canceled, expired or forfeited, number of shares (in shares) (1,697)    
Canceled, expired or forfeited, weighted average exercise price (in dollars per share) $ 285.56    
Outstanding ending balance, number of shares (in shares) 192,380    
Outstanding ending balance, weighted average exercise price (in dollars per share) $ 264.39    
Nonvested, number of shares (in shares) 192,380   135,916
Expected, number of shares (in shares) [1] 76,002    
[1] Includes estimated performance achievement