Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Additional Information (Detail)

v2.4.0.8
Share-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified
0 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]            
Share-based compensation expense   $ 11.0 $ 6.6 $ 34.4 $ 21.9  
Unrecognized compensation cost on non-vested stock awards 64.3 64.3   64.3    
Unrecognized compensation cost on non-vested stock awards, weighted-average period of recognition 1 year 7 months 6 days          
Weighted-average grant date fair value of SARs granted   $ 20.88 $ 0.00 $ 25.71 $ 11.85  
Total intrinsic value of awards exercised for options and SARs   2.4 0.1 37.4 0.3  
Total vesting date fair value of stock units   0.2 0.4 8.7 7.2  
Unrealized excess tax benefits $ 21.1 $ 21.1   $ 21.1   $ 15.4