Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Details 1)

v3.8.0.1
Stock Plans (Details 1) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Goods and Nonemployee Services Transaction [Line Items]    
Weighted-average risk-free interest rate 2.75% 2.16%
Expected dividend payments $ 0 $ 0
Expected holding period (years) [1] 6 years 4 months 24 days 6 years 7 months 6 days
Weighted-average volatility factor [2] 0.89% 0.88%
Estimated forfeiture rates for options granted [3] 26.00% 28.00%
[1] Expected holding period is based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and the expectations of future employee behavior.
[2] Weighted average volatility is based on the historical volatility of our common stock.
[3] Estimated forfeiture rates are based on historical data.