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Capital Stock - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Class of Stock [Line Items]      
Common stock, shares authorized 750,000,000 750,000,000  
Common stock, par value $ 0.01 $ 0.01  
Percentage of increase in quarterly cash dividend 11.00%    
Dividend declared, per share $ 0.20    
Preferred stock, shares authorized 60,000,000    
Preferred stock, par value $ 0.01    
Common stock repurchases 3,393,462 8,807,515  
Treasury stock purchases $ 214.8 $ 424.5 $ 51.7
Stock repurchase program, remaining authorized repurchase amount $ 558.4