Assumptions to Estimate Fair Value for Stock Options at Grant Date (Detail) - Time Vested Stock Options |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Risk-free interest rate, minimum | 1.01% | 1.15% | 0.86% | 1.13% |
Risk-free interest rate, maximum | 1.56% | 1.15% | 1.56% | |
Expected volatility, minimum | 57.00% | 59.00% | 57.00% | 59.00% |
Expected volatility, maximum | 60.00% | 58.00% | 65.00% | |
Minimum | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected life (in years) | 4 years | 4 years | 4 years | 4 years |
Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |
Maximum | ||||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected life (in years) | 6 years 3 months | 6 years 3 months | 6 years 3 months | |
Expected dividend yield | 0.36% |