Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Additional Information (Detail)

v3.7.0.1
Share-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation expense   $ 11.4 $ 10.7 $ 22.7 $ 20.5
Unrecognized compensation cost on non-vested stock awards $ 64.9 64.9   $ 64.9  
Unrecognized compensation cost on non-vested stock awards, weighted-average period of recognition       1 year 7 months 6 days  
Total vesting date fair value of stock units   $ 1.4 $ 1.8 $ 1.4 $ 1.8
SARs [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Weighted-average grant date fair value of SARs granted   $ 34.76 $ 29.77 $ 28.34 $ 29.47
Total intrinsic value of awards exercised for SARs   $ 80.2 $ 8.2 $ 97.0 $ 14.1
Performance conditions [Member] | Chief Executive Officer [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock unit awards vesting date Dec. 31, 2019        
Performance conditions [Member] | Minimum [Member] | Chief Executive Officer [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Performance stock unit awards vesting percentage 0.00%        
Performance conditions [Member] | Maximum [Member] | Chief Executive Officer [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Performance stock unit awards vesting percentage 200.00%