XML 39 R29.htm IDEA: XBRL DOCUMENT v3.10.0.1
Stock-Based Compensation (Tables)
9 Months Ended
Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Schedule of weighted average assumptions
The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below:
 
Three Months Ended September 30,
 
Nine Months Ended September 30,
 
2018
 
2017
 
2018
 
2017
Risk-free interest rate
2.86%
 
1.96%
 
2.73%
 
2.21%
Expected volatility
71%
 
73%
 
72%
 
73%
Expected life in years
6.1
 
6.1
 
6.2
 
6.0
Dividend yield