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Net Income per Share - Share Repurchase Programs (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Oct. 01, 2016
Sep. 30, 2017
Oct. 01, 2016
May 03, 2017
Mar. 21, 2016
Share Repurchase Program            
Share repurchase program, amount authorized to be repurchased         $ 20.0 $ 20.0
Number of shares repurchased and retired 165,629 110,908 554,708 783,703    
Average repurchase price per share (in dollars per share) $ 36.63 $ 25.84 $ 35.23 $ 24.33    
Amount available for future repurchases $ 9.5   $ 9.5