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Stock-Based Compensation - Additional Information (Detail)
$ in Millions
9 Months Ended
Sep. 30, 2017
USD ($)
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Unrecognized stock-based compensation expense | $ $ 56.8
Weighted-average period of recognition of unrecognized stock-based compensation expense (in years) 2 years 1 month 6 days
Employees | Common Stock  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Shares issued 1,299,000
Non-employee directors | Common Stock  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Shares issued 18,000
RSUs | Employees  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of shares granted, RSUs 1,052,000
Fair value of shares granted | $ $ 47.5
RSUs granted in connection with the 2016 CICP 175,000
Percentage of target incentive compensation eligible to be elected and received by employees in the form of RSUs 50.00%
Restricted stock compensation expense | $ $ 7.7
Total stock-based compensation, period of recognition 1 year
Nonqualified Stock Options | Employees  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Fair value of shares granted | $ $ 20.6
Number of shares granted, options 1,520,000