Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Details 4) (Stock Options, USD $)
12 Months Ended
Dec. 31, 2013
Options Outstanding  
Number of Underlying Shares 4,905,214
Options Exercisable  
Number of Underlying Shares 3,285,695
0.26-1.30
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 0.26
Range of Exercise Price, high end of range (in dollars per share) $ 1.30
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 0.57
Number of Underlying Shares 187,284
Weighted-Average Remaining Contractual Life 1 year
Options Exercisable  
Number of Underlying Shares 187,284
Weighted-Average Remaining Contractual Life 1 year
1.35-2.60
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 1.35
Range of Exercise Price, high end of range (in dollars per share) $ 2.60
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 2.18
Number of Underlying Shares 473,347
Weighted-Average Remaining Contractual Life 2 years 6 months
Options Exercisable  
Number of Underlying Shares 473,347
Weighted-Average Remaining Contractual Life 2 years 6 months
2.65-3.90
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 2.65
Range of Exercise Price, high end of range (in dollars per share) $ 3.90
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 3.23
Number of Underlying Shares 325,523
Weighted-Average Remaining Contractual Life 3 years 7 months 6 days
Options Exercisable  
Number of Underlying Shares 325,523
Weighted-Average Remaining Contractual Life 3 years 7 months 6 days
3.95-5.20
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 3.95
Range of Exercise Price, high end of range (in dollars per share) $ 5.20
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 4.87
Number of Underlying Shares 941,827
Weighted-Average Remaining Contractual Life 5 years 2 months 12 days
Options Exercisable  
Number of Underlying Shares 937,785
Weighted-Average Remaining Contractual Life 5 years 2 months 12 days
5.25-6.50
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 5.25
Range of Exercise Price, high end of range (in dollars per share) $ 6.50
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 6.19
Number of Underlying Shares 1,686,513
Weighted-Average Remaining Contractual Life 7 years 8 months 12 days
Options Exercisable  
Number of Underlying Shares 1,033,886
Weighted-Average Remaining Contractual Life 7 years 8 months 12 days
6.55-7.80
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 6.55
Range of Exercise Price, high end of range (in dollars per share) $ 7.80
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 7.49
Number of Underlying Shares 118,947
Weighted-Average Remaining Contractual Life 6 years 6 months
Options Exercisable  
Number of Underlying Shares 100,620
Weighted-Average Remaining Contractual Life 6 years 6 months
7.85-9.10
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 7.85
Range of Exercise Price, high end of range (in dollars per share) $ 9.10
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 8.84
Number of Underlying Shares 238,451
Weighted-Average Remaining Contractual Life 8 years 6 months
Options Exercisable  
Number of Underlying Shares 94,534
Weighted-Average Remaining Contractual Life 8 years 6 months
9.15-22.77
 
Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)  
Range of Exercise Price, low end of range (in dollars per share) $ 9.15
Range of Exercise Price, high end of range (in dollars per share) $ 22.77
Options Outstanding  
Weighted Average Exercise Price (in dollars per share) $ 11.54
Number of Underlying Shares 933,322
Weighted-Average Remaining Contractual Life 8 years 8 months 12 days
Options Exercisable  
Number of Underlying Shares 132,716
Weighted-Average Remaining Contractual Life 8 years 10 months 24 days