XML 94 R79.htm IDEA: XBRL DOCUMENT v3.7.0.1
Summary of Employee and Director Stock Option Highlights (Detail) - Employee And Director Stock Option - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Compensation expense $ 2.8 $ 1.9 $ 4.6 $ 3.5
Intrinsic value of stock options exercised 5.6 4.7 10.1 6.0
Tax benefit recognized from stock option exercises $ 2.2 $ 1.7 $ 3.9 $ 2.1