Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Details 1)

v3.10.0.1
Stock Plans (Details 1) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Goods and Nonemployee Services Transaction [Line Items]        
Weighted-average risk-free interest rate 2.90% 2.00% 2.70% 2.10%
Expected dividend payments $ 0 $ 0 $ 0 $ 0
Expected holding period (years) [1] 6 years 4 months 24 days 6 years 6 months 6 years 4 months 24 days 6 years 6 months
Weighted-average volatility factor [2] 0.91% 0.88% 0.89% 0.88%
Estimated forfeiture rates [3] 25.00% 27.00% 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.