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Summary of Significant Accounting Policies (Stock Option Valuation Assumptions) (Details) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Accounting Policies [Abstract]      
Expected stock price volatility 49.06% 54.14% 73.75%
Annual dividend rate 0.00% 0.00% 0.00%
Risk-free interest rate 1.59% 1.6429% 1.4038%
Expected option life (in years) 5 years 3 months 11 days 5 years 4 months 24 days 5 years 3 months 11 days
Estimated fair value per share $ 9.06 $ 5.70 $ 6.09