Equity Compensation (Activity) (Details) - Stock options - $ / shares
9 Months Ended
Jan. 01, 2017
Sep. 30, 2017
Jun. 11, 2013
Shares Subject to Options Outstanding      
Balance at the beginning of the period (in shares) 3,776,405 3,776,405  
Exercised (in shares)   (1,111,583)  
Expired (in shares)   (59,552)  
Forfeited (in shares)   (26,045)  
Balance at the end of the period (in shares)   2,579,225  
Exercisable options (in shares)   2,201,595  
Vested and expected to vest at the end of the period (in shares)   2,579,225  
Weighted Average Exercise Price      
Balance at the beginning of the period (in dollars per share) $ 11.55 $ 11.55  
Exercised (in dollars per share)   10.16  
Expired (in dollars per share)   17.50  
Forfeited (in dollars per share)   16.82  
Balance at the end of the period (in dollars per share)   11.95  
Exercisable options at the end of the period (in dollars per share)   11.58  
Vested and expected to vest (in dollars per share)   $ 11.95  
Weighted-Average Remaining Contractual Life      
Exercisable options   5 years 2 months 12 days  
Vested and expected to vest   5 years 6 months  
2013 Plan      
Stock options      
Potential 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 1,186,489