Fair Value of Options Granted, Excluding Stock Option Grant Program of Nonemployee Directors and Executives, Estimated at Date of Grant Using Black Scholes Merton Option Pricing Model (Detail) - $ / shares |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
|
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected volatility, minimum | 55.00% | 55.00% | 55.00% | 53.00% |
Expected volatility, maximum | 56.00% | 55.00% | ||
Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |
Risk-free interest rate, minimum | 1.03% | 1.46% | 1.03% | 1.29% |
Risk-free interest rate, maximum | 1.19% | 1.60% | 1.48% | 1.60% |
Weighted-average fair value of options granted | $ 11.11 | $ 20.88 | $ 13.98 | $ 14.40 |
Minimum | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Weighted-average expected life | 3 years 6 months | 4 years 6 months 29 days | 3 years 6 months | 4 years 6 months 29 days |
Maximum | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Weighted-average expected life | 4 years 6 months 29 days |