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Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 01, 2024
USD ($)
shares
Mar. 15, 2023
USD ($)
shares
May 10, 2022
shares
Mar. 15, 2022
USD ($)
shares
Dec. 31, 2024
USD ($)
shares
Sep. 30, 2024
shares
Jun. 30, 2024
shares
Mar. 31, 2024
shares
Mar. 31, 2023
shares
Mar. 31, 2022
shares
Dec. 31, 2024
USD ($)
TIME
shares
Dec. 31, 2023
USD ($)
shares
Dec. 31, 2022
USD ($)
shares
Dec. 31, 2021
USD ($)
Mar. 16, 2021
USD ($)
shares
Restricted Stock Units (RSUs) [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares granted in the period         2,300 700 800 344,600 390,000 641,000 355,245 396,913 650,355    
Share based payment award vesting date               Mar. 01, 2029 Mar. 15, 2028 Mar. 15, 2027          
Period of service from grant date stock options awarded not subject to forfeiture               2 years 2 years 2 years          
Restricted stock or unit expense | $                     $ 53.8 $ 43.4 $ 36.4    
Restricted Stock Units (RSUs) [Member] | Executive Officer [Member] | Minimum [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Minimum age of employee with not subject to award forfeiture on condition compliance               55 years 55 years 55 years          
Unvested Restricted Stock [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Total intrinsic value | $         $ 548.9           548.9 468.5      
Equity awards with an aggregate fair value | $                     93.5 62.2      
Performance Shares [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Restricted stock or unit expense | $                     22.0 20.0 15.2    
Total intrinsic value | $         $ 93.0           93.0 75.2      
Equity awards with an aggregate fair value | $                     $ 31.6 $ 28.9 21.8    
Performance share awards approved, Fair value | $ $ 14.2 $ 10.3   $ 8.6                      
Vesting period, years 3 years 3 years   3 years                      
2017 Performance Share Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional awards, terms                     The 2024, 2023 and 2022 awards are subject to a three-year performance period that began on January 1, 2024, 2023 and 2022, respectively, and vest on the three-year anniversary of the date of grant (March 1, 2027, March 15, 2026 and March 15, 2025).        
Cash Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares granted in the period                     0 0      
Cash Awards [Member] | Officer and Key Employees [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional awards, terms                     The ultimate award value will be equal to the trailing twelve‑month price of our common stock, multiplied by the number of units subject to the award, but limited to between 0.5 and 1.5 times the original value of the units determined as of the grant date.        
Vesting period, years                     3 years        
Provisional compensation cash awards approved for future grant by compensation committee, value | $       $ 19.9                     $ 18.8
Provisional compensation cash award approved for future grant by compensation committee, units       125,000                     147,000
Performance awards period, years                     1 year        
Ultimate award value, multiples of original value of the units, minimum | TIME                     0.5        
Ultimate award value, multiples of original value of the units, maximum | TIME                     1.5        
2022 Provisional Cash Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Cash-based compensation awards, expenses | $                     $ 13.2 $ 13.4 0.0    
Performance awards expiration date                     Jan. 01, 2025        
2022 Provisional Cash Awards [Member] | Officer and Key Employees [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional compensation cash award approved for future grant by compensation committee, units                 122,000            
2021 Provisional Cash Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional compensation cash award approved for future grant by compensation committee, units         129,000           129,000        
Cash-based compensation awards, expenses | $                       $ 13.1 $ 12.4 $ 0.0  
Performance awards expiration date                     Jan. 01, 2024        
Cash award with aggregate fair value vested and distributed to participants | $                     $ 25.4        
2021 Provisional Cash Awards [Member] | Officer and Key Employees [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional compensation cash award approved for future grant by compensation committee, units                   143,000          
2020 Provisional Cash Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional compensation cash award approved for future grant by compensation committee, units                       191,000      
Cash award with aggregate fair value vested and distributed to participants | $                       $ 24.7      
2019 Provisional Cash Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Provisional compensation cash award approved for future grant by compensation committee, units                         177,000    
Cash award with aggregate fair value vested and distributed to participants | $                         $ 21.1    
Long Term Incentive Plan [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares available for grant         11,100,000           11,100,000        
Shares granted in the period     3,500,000               2,500,000        
Long Term Incentive Plan [Member] | Officer and Key Employees [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares available for grant 1,044,000 1,131,000                          
Long Term Incentive Plan [Member] | Restricted Stock, Restricted Stock Units and Performance Unit Awards [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares authorized         4,000,000           4,000,000        
Shares available for grant         2,500,000           2,500,000        
Long Term Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares granted in the period                     355,245 396,913 650,355    
Fair value of grants in period | $                     $ 85.1 $ 67.0 $ 99.4    
Long Term Incentive Plan [Member] | Performance Shares [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Shares authorized 58,000 58,000   54,000                      
Long Term Incentive Plan [Member] | Performance Shares [Member] | Executive Officer [Member] | Minimum [Member]                              
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                              
Minimum age of employee with not subject to award forfeiture on condition compliance 62 years 55 years   55 years                      
Period of service from grant date stock options awarded not subject to forfeiture   2 years   2 years