Equity Compensation (Details 2) (Stock options, USD $)
12 Months Ended
Dec. 31, 2014
Options Outstanding  
Number of Underlying Shares 4,851,221
Options Exercisable  
Number of Underlying Shares 2,494,711
0.78-1.72  
Equity compensation  
Range of Exercise Price, low end of range (in dollars per share) $ 0.78
Range of Exercise Price, high end of range (in dollars per share) $ 1.72
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 1.10
Number of Underlying Shares 37,399
Weighted-Average Remaining Contractual Life 9 months 18 days
Options Exercisable  
Number of Underlying Shares 37,399
Weighted-Average Remaining Contractual Life 9 months 18 days
1.97-3.38  
Equity compensation  
Range of Exercise Price, low end of range (in dollars per share) $ 1.97
Range of Exercise Price, high end of range (in dollars per share) $ 3.38
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 2.57
Number of Underlying Shares 248,746
Weighted-Average Remaining Contractual Life 1 year 10 months 24 days
Options Exercisable  
Number of Underlying Shares 248,746
Weighted-Average Remaining Contractual Life 1 year 10 months 24 days
3.58-6.14  
Equity compensation  
Range of Exercise Price, low end of range (in dollars per share) $ 3.58
Range of Exercise Price, high end of range (in dollars per share) $ 6.14
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 5.64
Number of Underlying Shares 1,570,282
Weighted-Average Remaining Contractual Life 5 years 8 months 12 days
Options Exercisable  
Number of Underlying Shares 1,416,661
Weighted-Average Remaining Contractual Life 5 years 7 months 6 days
6.34-9.94  
Equity compensation  
Range of Exercise Price, low end of range (in dollars per share) $ 6.34
Range of Exercise Price, high end of range (in dollars per share) $ 9.94
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 8.27
Number of Underlying Shares 1,007,227
Weighted-Average Remaining Contractual Life 7 years 2 months 12 days
Options Exercisable  
Number of Underlying Shares 627,128
Weighted-Average Remaining Contractual Life 7 years 1 month 6 days
11.28-16.97  
Equity compensation  
Range of Exercise Price, low end of range (in dollars per share) $ 11.28
Range of Exercise Price, high end of range (in dollars per share) $ 16.97
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 13.94
Number of Underlying Shares 1,180,368
Weighted-Average Remaining Contractual Life 9 years
Options Exercisable  
Number of Underlying Shares 143,901
Weighted-Average Remaining Contractual Life 6 years 3 months 18 days
17.66-22.92  
Equity compensation  
Range of Exercise Price, low end of range (in dollars per share) $ 17.66
Range of Exercise Price, high end of range (in dollars per share) $ 22.92
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 21.00
Number of Underlying Shares 807,199
Weighted-Average Remaining Contractual Life 9 years 1 month 6 days
Options Exercisable  
Number of Underlying Shares 20,876
Weighted-Average Remaining Contractual Life 8 years 1 month 6 days