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Stock-Based Compensation (Schedule of Fair Value of Employee Share-Based Payments Awards Estimated Using the Assumptions) (Details)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Stock Option [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 1.62% 1.16%
Dividend yield 0.00% 0.00%
Expected volatility 64.00% 79.00%
Expected life 4 years 4 years 4 months 6 days
Employee Stock Purchase Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 0.62% 0.51%
Dividend yield 0.00% 0.00%
Expected volatility 68.00% 81.00%
Expected life 6 months 6 months