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Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail)
 3 Months Ended 12 Months Ended
Mar. 16, 2017
USD ($)
shares
Mar. 17, 2016
USD ($)
shares
Mar. 11, 2015
USD ($)
shares
Mar. 31, 2017
shares
Mar. 31, 2016
shares
Mar. 31, 2015
shares
Dec. 31, 2017
USD ($)
Times
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2015
USD ($)
shares
Dec. 31, 2014
USD ($)
shares
Mar. 12, 2014
USD ($)
shares
May 12, 2009
shares
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Share-based compensation, shares outstanding | shares             10,600,000 10,300,000 8,800,000 8,400,000    
Shares granted in the period | shares             476,350 479,167 394,975      
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          
Share-based compensation, shares outstanding | shares             4,000,000          
Shares granted in the period | shares             4,000,000          
Restricted Stock Plan [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Shares authorized | shares                       4,000,000
Shares granted in the period | shares       477,500 466,600 362,600            
Restricted Stock Units (RSUs) [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Shares granted in the period | shares             476,350 479,167 394,975      
Fair value of grants in period             $ 26,800,000 $ 20,400,000 $ 16,700,000      
Restricted stock or unit expense             $ 19,600,000 $ 18,200,000 $ 14,400,000      
Restricted Stock Units (RSUs) [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Share based payment award vesting date       Mar. 19, 2022 Mar. 17, 2021 Mar. 11, 2020            
Restricted Stock Units (RSUs) [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      
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             $ 109,300,000 $ 80,000,000        
Equity awards with an aggregate fair value             $ 23,300,000 14,200,000        
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, 2019, 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.          
Performance awards period, years             1 year          
Vesting period, years             2 years          
Provisional compensation cash awards approved for future grant by compensation committee, value $ 14,300,000                      
Provisional compensation cash award approved for future grant by compensation committee, units | shares 255,000                      
Ultimate award value, multiples of original value of the units, minimum | Times             0.5          
Ultimate award value, multiples of original value of the units, maximum | Times             1.5          
2017 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             242,000          
Cash-based compensation awards, expenses             $ 0          
Performance Shares [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Shares authorized | shares 86,250 72,900 53,900                  
Total intrinsic value             $ 10,700,000          
Performance unit awards approved, Fair value $ 4,900,000 $ 3,200,000 $ 2,500,000                  
Provisional awards, terms             Granted units for the 2017 provisional awards will fully vest based on continuous employment through March 16, 2020 and will be settled in shares of our common stock on a one-for-one basis as soon as practicable thereafter.          
Performance awards period, years             1 year          
Vesting period, years             2 years          
Compensation expense             $ 3,300,000 2,900,000        
2017 Performance Share Awards [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Provisional awards, terms             The 2017 awards are subject to a three-year performance period that begins on January 1, 2017, and vest on the three-year anniversary of the date of grant (March 16, 2020).          
Performance awards period, years             3 years          
Vesting period, years             3 years          
Performance awards expiration date             Mar. 16, 2020          
2016 Provisional Cash Awards [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Cash-based compensation awards, expenses             $ 10,600,000          
2016 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   $ 17,400,000                    
Provisional compensation cash award approved for future grant by compensation committee, units | shares   397,000   385,000                
2015 Provisional Cash Awards [Member]                        
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]                        
Cash-based compensation awards, expenses             $ 9,300,000 6,600,000        
2015 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     $ 14,600,000                  
Provisional compensation cash award approved for future grant by compensation committee, units | shares     315,000   294,000              
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               $ 4,500,000 $ 4,900,000 $ 0    
Grants vested in period fair value             $ 9,300,000          
2014 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                     $ 10,800,000  
Provisional compensation cash award approved for future grant by compensation committee, units | shares           220,000         229,000  
2012 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                 342,000      
Grants vested in period fair value                 $ 15,800,000      
2011 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                   411,000    
Grants vested in period fair value                   $ 17,600,000    
2013 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               246,000        
Cash-based compensation awards, expenses               $ 11,200,000