Stock Option Plan - Fair Value Assumptions (Details) |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
Employee Stock | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Remaining contractual term (in years) | 6 months | 6 months | |
Expected volatility | 63.40% | 46.80% | |
Risk-free interest rate | 0.20% | 0.10% | |
Expected dividend rate | 0.00% | 0.00% | |
Employee Stock Option | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Remaining contractual term (in years) | 6 years | 6 years | 6 years |
Expected volatility | 62.20% | 57.40% | 59.10% |
Risk-free interest rate | 1.60% | 1.90% | 1.30% |
Expected dividend rate | 0.00% | 0.00% | 0.00% |
Non-employee Stock Options | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Remaining contractual term (in years) | 8 years 2 months 18 days | 7 years 3 months 18 days | 9 years |
Expected volatility | 73.00% | 56.10% | 58.80% |
Risk-free interest rate | 2.00% | 2.10% | 2.70% |
Expected dividend rate | 0.00% | 0.00% | 0.00% |