Equity Compensation (Activity) (Details) - Stock options - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Jun. 11, 2013
Shares Subject to Options Outstanding      
Balance at the beginning of the period (in shares) 4,851,221 4,905,214  
Granted (in shares) 238,516 1,592,268  
Exercised (in shares) (285,387) (1,512,514)  
Expired (in shares) (47,866) (136)  
Forfeited (in shares) (183,812) (133,611)  
Balance at the end of the period (in shares) 4,572,672 4,851,221  
Exercisable options (in shares) 3,185,180 2,494,711  
Vested and expected to vest at the end of the period (in shares) 4,466,655 4,615,485  
Weighted Average Grant Date Fair Value      
Granted (in dollars per share) $ 5.310 $ 9.99  
Weighted Average Exercise Price      
Balance at the beginning of the period (in dollars per share) 10.57 6.31  
Granted (in dollars per share) 10.52 18.00  
Exercised (in dollars per share) 4.87 4.24  
Expired (in dollars per share) 13.92 7.40  
Forfeited (in dollars per share) 14.76 13.77  
Balance at the end of the period (in dollars per share) 10.72 10.57  
Exercisable options at the end of the period (in dollars per share) 8.76 6.33  
Vested and expected to vest (in dollars per share) $ 10.61 $ 10.30  
Weighted-Average Remaining Contractual Life      
Exercisable options 5 years 2 months 12 days 5 years 7 months 6 days  
Vested and expected to vest 6 years 1 month 6 days 7 years  
2013 Plan      
Stock options      
Annual increase in shares authorized for issuance as a percentage of shares outstanding as of the preceding December 31     5.00%