Equity Compensation (Activity) (Details) - Stock options - $ / shares
6 Months Ended
Jan. 01, 2015
Jun. 30, 2015
Jun. 11, 2013
Shares Subject to Options Outstanding      
Balance at the beginning of the period (in shares) 4,851,221 4,851,221  
Granted (in shares)   166,916  
Exercised (in shares)   (151,776)  
Expired (in shares)   (5,364)  
Forfeited (in shares)   (38,736)  
Balance at the end of the period (in shares)   4,822,261  
Exercisable options (in shares)   2,856,014  
Vested and expected to vest at the end of the period (in shares)   4,666,097  
Weighted Average Grant Date Fair Value      
Granted (in dollars per share)   $ 5.88  
Weighted Average Exercise Price      
Balance at the beginning of the period (in dollars per share) $ 10.57 10.57  
Granted (in dollars per share)   11.64  
Exercised (in dollars per share)   4.89  
Expired (in dollars per share)   11.82  
Forfeited (in dollars per share)   13.92  
Balance at the end of the period (in dollars per share)   10.76  
Exercisable options at the end of the period (in dollars per share)   7.84  
Vested and expected to vest (in dollars per share)   $ 10.59  
Weighted-Average Remaining Contractual Life      
Exercisable options   5 years 7 months 6 days  
Vested and expected to vest   6 years 8 months 12 days  
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%
Increase in number of shares authorized for issuance 1,215,269