v3.26.3
Note 9 - Equity Compensation Plans - Summary of Stock Activity (Details) - USD ($)
$ / shares in Units, $ in Millions
 9 Months Ended
Sep. 30, 2026
Sep. 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 $ 19.8   $ 72.6
Granted, options (in shares) 299,367    
Weighted average grant price (in dollars per share) $ 219.84 $ 273.6  
Dividend reinvestment, options (in shares) 0    
Dividend reinvestment, options, weighted average exercise price (in (in dollars per share)    
Exercised or lapsed, options (in shares) (197,219)    
Exercised or lapsed, options, weighted average exercise price (in dollars per share) $ 134.7    
Exercised or lapsed, options, aggregate intrinsic value $ 11.9    
Canceled, expired or forfeited, option (in shares) (68,299)    
Canceled, expired or forfeited, options, weighted average exercise price (in dollars per share) $ 227.49    
Outstanding, option (in shares) 1,710,189    
Outstanding beginning balance, options, weighted average exercise price (in dollars per share) $ 190.69    
Exercisable, options (in shares) 1,163,169   1,178,052
Exercisable, options, weighted average exercise price (in dollars per share) $ 170.92   $ 156.76
Exercisable, options, aggregate intrinsic value $ 19.8   $ 78.8
Nonvested, options (in shares) 547,020    
Expected to vest, options (in shares) 471,905    
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) 197,684    
Granted, weighted average exercise price (in dollars per share) $ 218.96    
Dividend reinvestment, number of shares (in shares) 0    
Dividend reinvestment (in dollars per share)    
Exercised or lapsed, number of shares (in shares) (132,515)    
Exercised or lapsed, weighted average exercise price (in dollars per share) $ 228.22    
Canceled, expired or forfeited, number of shares (in shares) (24,224)    
Canceled, expired or forfeited, weighted average exercise price (in dollars per share) $ 237.49    
Outstanding ending balance, number of shares (in shares) 362,892    
Outstanding ending balance, weighted average exercise price (in dollars per share) $ 233.52    
Nonvested, number of shares (in shares) 362,892   321,947
Expected, number of shares (in shares) 321,899    
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) 103,399    
Granted, weighted average exercise price (in dollars per share) $ 224.02    
Dividend reinvestment, number of shares (in shares) 1,411    
Exercised or lapsed, number of shares (in shares) (51,718)    
Exercised or lapsed, weighted average exercise price (in dollars per share) $ 211.19    
Canceled, expired or forfeited, number of shares (in shares) (7,687)    
Canceled, expired or forfeited, weighted average exercise price (in dollars per share) $ 272.46    
Outstanding ending balance, number of shares (in shares) 181,321    
Outstanding ending balance, weighted average exercise price (in dollars per share) $ 268.53    
Nonvested, number of shares (in shares) 181,321   135,916
Expected, number of shares (in shares) [1] 77,203    
[1] Includes estimated performance achievement