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Stock-Based Compensation (Valuation Assumptions) (Details) - Stock options [Member] - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected term (in years) (1) 5 years 2 months 6 years 6 years 6 years
Volatility 67.00% 68.00% 66.00% 65.00%
Risk-free interest rate 1.64% 1.91% 1.70% 1.915%
Dividend yield 0.00% 0.00% 0.00% 0.00%
Weighted-average estimated fair value of stock options granted $ 2.31 $ 1.43 $ 2.09 $ 1.20