Stock-Based Compensation (Details 1) (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]  
Options Outstanding, Shares, Beginning of Period 8,515,879
Options Outstanding, Shares, Options exercised (1,063,082)
Options Outstanding, Shares, forfeited (31,189)
Options Outstanding, Shares, End of Period 7,421,608
Options Outstanding, Shares, Vested and Expected to Vest 7,352,543
Options Outstanding, Shares, Exercisable 4,460,131
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]  
Options Outstanding, Weighted Average Exercise Price, Beginning of Period, USD per share $ 8.76
Options Outstanding, Weighted Average Exercise Price, Options exercised, USD per share $ 7.85
Options Outstanding, Weighted Average Exercise Price, Options forfeited, USD per share $ 15.50
Options Outstanding, Weighted Average Exercise Price, End of Period, USD per share $ 8.86
Options Outstanding, Weighted Average Exercise Price Per Share, Vested and Expected to Vest, USD per share $ 8.81
Options Outstanding, Weighted Average Exercise Price Per Share, Exercisable, USD per share $ 7.03
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]  
Options Outstanding, Weighted Average Remaining Contractual Term, End of Period (in years) 6 years 9 months 7 days
Options Outstanding, Weighted Average Remaining Contractual Term, Vested and Expected to Vest (in years) 6 years 9 months 3 days
Options Outstanding, Weighted Average Remaining Contractual Term, Exercisable (in years) 6 years 2 months 26 days
Options Outstanding, Aggregate Intrinsic Value, End of Period $ 620,865
Options Outstanding, Aggregate Intrinsic Value, Vested and Expected to Vest 615,461
Options Outstanding, Aggregate Intrinsic Value, Exercisable $ 381,286