Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Additional Information (Detail)

v3.10.0.1
Share-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense $ 10.4 $ 11.4 $ 20.2 $ 22.7
Unrecognized compensation cost on non-vested stock awards 73.9   $ 73.9  
Unrecognized compensation cost on non-vested stock awards, weighted-average period of recognition     1 year 4 months 24 days  
Weighted-average grant date fair value of SARs granted     $ 43.57  
Total vesting date fair value of stock units $ 2.1 $ 1.4 $ 2.1 $ 1.4
SARs [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
SARs granted 0   0  
Weighted-average grant date fair value of SARs granted   $ 17.38   $ 14.17
Total intrinsic value of awards exercised for SARs $ 64.8 $ 80.2 $ 187.0 $ 97.0