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Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail)
 3 Months Ended 12 Months Ended
Mar. 12, 2020
USD ($)
shares
Mar. 14, 2019
USD ($)
shares
Mar. 15, 2018
USD ($)
shares
Mar. 16, 2017
USD ($)
shares
Mar. 17, 2016
USD ($)
shares
Mar. 31, 2020
shares
Mar. 31, 2019
shares
Mar. 31, 2018
shares
Dec. 31, 2020
USD ($)
TIME
shares
Dec. 31, 2019
USD ($)
shares
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
shares
Mar. 31, 2017
shares
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Share-based compensation, shares outstanding | shares                 7,500,000 7,900,000 8,800,000    
Officer and Key Employees [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Performance awards period, years 1 year                        
Restricted Stock Units (RSUs) [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Shares granted in the period | shares           405,870 399,900 420,200 422,610 414,700 439,100    
Fair value of grants in period                 $ 34,900,000 $ 31,800,000 $ 28,700,000    
Share based payment award vesting date           Mar. 12, 2025 Mar. 14, 2024 Mar. 15, 2023          
Period of service from grant date stock options awarded not subject to forfeiture           2 years 2 years 2 years          
Restricted stock or unit expense                 $ 40,000,000.0 29,800,000 27,200,000    
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 55 years        
Unvested Restricted Stock [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Total intrinsic value                 $ 302,400,000 215,100,000      
Equity awards with an aggregate fair value                 2,000,000.0 2,100,000      
Performance Shares [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Equity awards with an aggregate fair value                 $ 12,500,000 5,700,000 3,700,000    
Shares authorized | shares 82,500 73,600 78,200                    
Performance share awards approved, Fair value $ 7,100,000 $ 5,800,000 $ 5,300,000                    
Vesting period, years                 2 years        
2017 Performance Share Awards [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Provisional awards, terms                 The 2020, 2019 and 2018 awards are subject to a three-year performance period that begins on January 1, 2020, 2019 and 2018, respectively, and vest on the three-year anniversary of the date of grant (March 12, 2023, March 14, 2022 and March 15, 2021).        
Cash-based compensation awards, expenses                   10,300,000 8,700,000    
Performance awards expiration date       Jan. 01, 2020                  
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 on December 31, 2022, 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 $ 18,400,000 $ 16,500,000   $ 14,300,000 $ 17,400,000                
Provisional compensation cash award approved for future grant by compensation committee, units | shares 213,000 206,800   255,000 397,000 200,000   242,000 209,000       385,000
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        
Cash-based compensation awards, expenses                 $ 0        
2020 Provisional Cash Awards [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Cash-based compensation awards, expenses                 $ 10,600,000        
Performance awards expiration date                 Jan. 01, 2023        
2019 Provisional Cash Awards [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Cash-based compensation awards, expenses                   0      
Performance awards expiration date                 Jan. 01, 2022        
2019 Provisional Cash Awards [Member] | Officer and Key Employees [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Provisional compensation cash awards approved for future grant by compensation committee, value     $ 15,000,000.0                    
Provisional compensation cash award approved for future grant by compensation committee, units | shares     219,000       190,000            
2018 Provisional Cash Awards [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Cash-based compensation awards, expenses                 $ 9,900,000 $ 8,900,000 0    
Performance awards expiration date     Jan. 01, 2021                    
2016 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 | shares                   341,000      
Cash-based compensation awards, expenses                   $ 22,400,000 $ 11,700,000    
Performance awards expiration date         Jan. 01, 2019                
2015 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 | shares                     269,000    
Cash-based compensation awards, expenses                     $ 15,800,000    
2014 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 | shares                       199,000  
Cash-based compensation awards, expenses                       $ 9,300,000  
Long Term Incentive Plan [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Share-based compensation, shares outstanding, Value                 $ 4,000,000.0        
Share-based compensation, shares outstanding | shares                 2,300,000        
Shares granted in the period | shares                 2,300,000        
Long Term Incentive Plan [Member] | Minimum [Member]                          
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                          
Period of service from grant date stock options awarded not subject to forfeiture                 2 years 2 years 2 years    
Long Term Incentive Plan [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