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Stock Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
May 13, 2013
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Feb. 07, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares authorized to issue grants (in shares)     26,963,150 26,963,150  
Shares available for grant (in shares)   277,821      
Tax benefits recorded on stock based compensation   $ 48.6 $ 35.0 $ 35.7  
Aggregate intrinsic value of options exercisable   $ 469.8      
Weighted average remaining contractual term of options exercisable (in years)   5 years      
Weighted-average remaining contractual life for options outstanding (in years)   6 years 10 months 28 days      
Shares, granted (in shares)   238,000 152,000 126,000  
2010 Equity Compensation Plan          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Increase in authorized number of shares of common stock (in shares) 6,500,000        
Restricted stock          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares authorized to issue grants (in shares)   26,963,150      
Shares, granted (in shares)   0 0 0  
Common Stock          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares authorized to issue grants (in shares)   13,250,000      
Subsequent Event | Common Stock          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares authorized to issue grants (in shares)         16,750,000