| Earnings Per Share |  
		
			7. Earnings Per Share
		 
			Net Income per Common Share
		 
			We calculate basic earnings per share by dividing net income by the weighted average number of common shares outstanding during the period. Diluted earnings per share is computed by dividing net income by the weighted average number of common shares outstanding adjusted for the dilutive effect of stock options. 
		 
			The following table shows the computation of basic and diluted earnings per share:
		 
			
				| 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						  | 
						     | 
						Thirteen Weeks Ended | 
						     | 
						Thirty-nine Weeks Ended |  
				| 
						  | 
						  | 
						September 28, | 
						  | 
						September 29, | 
						  | 
						September 28, | 
						  | 
						September 29, |  
				| 
						(in thousands, except share and per share data) | 
						  | 
						2017 | 
						     | 
						2016 | 
						  | 
						2017 | 
						     | 
						2016 |  
				| 
						Net income | 
						  | 
						$ | 
						 23,255 | 
						  | 
						$ | 
						 14,219 | 
						  | 
						$ | 
						 54,812 | 
						  | 
						$ | 
						 26,332 |  
				| 
						Basic weighted average shares outstanding | 
						  | 
						  | 
						 94,439,204 | 
						  | 
						  | 
						 83,457,037 | 
						  | 
						  | 
						 89,613,542 | 
						  | 
						  | 
						 83,405,904 |  
				| 
						Dilutive effect of share based awards | 
						  | 
						  | 
						 9,460,398 | 
						  | 
						  | 
						 4,911,652 | 
						  | 
						  | 
						 8,452,267 | 
						  | 
						  | 
						 4,846,287 |  
				| 
						Diluted weighted average shares outstanding | 
						  | 
						  | 
						 103,899,602 | 
						  | 
						  | 
						 88,368,689 | 
						  | 
						  | 
						 98,065,809 | 
						  | 
						  | 
						 88,252,191 |  
				| 
						Basic earnings per share | 
						  | 
						$ | 
						 0.25 | 
						  | 
						$ | 
						 0.17 | 
						  | 
						$ | 
						 0.61 | 
						  | 
						$ | 
						 0.32 |  
				| 
						Diluted earnings per share | 
						  | 
						$ | 
						 0.22 | 
						  | 
						$ | 
						 0.16 | 
						  | 
						$ | 
						 0.56 | 
						  | 
						$ | 
						 0.30 | 
			 
		 
			The following awards have been excluded from the computation of dilutive effect of share based awards because the effect would be anti‑dilutive:
		 
			
				| 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  | 
						  |  
				| 
						  | 
						     | 
						Thirteen Weeks Ended | 
						     | 
						Thirty-nine Weeks Ended |  
				| 
						  | 
						  | 
						September 28, | 
						  | 
						September 29, | 
						  | 
						September 28, | 
						  | 
						September 29, |  
				| 
						  | 
						  | 
						2017 | 
						  | 
						2016 | 
						  | 
						2017 | 
						  | 
						2016 |  
				| 
						Stock Options | 
						  | 
						 11,664 | 
						  | 
						 1,903,466 | 
						  | 
						 717,685 | 
						  | 
						 2,332,976 | 
			 
		 |  
		
			9. Earnings Per Share
		 
			Net Income per Common Share
		 
			              We calculate basic earnings per share by dividing net income by the weighted average number of common shares outstanding during the period. Diluted earnings per share is computed by dividing net income by the weighted average number of common shares outstanding adjusted for the dilutive effect of stock options. The following table shows the computation of basic and diluted earnings per share:
		 
			                                                                                                                                                                                    
		 
			
				| 
						  | 
						  | 
						Year EndedDecember 25,
 2014
 | 
						  | 
						Year EndedDecember 31,
 2015
 | 
						  | 
						Year EndedDecember 29,
 2016
 | 
						  |  
				| 
						Net income (in thousands) | 
						  | 
						$ | 15,098 | 
						  | 
						$ | 26,807 | 
						  | 
						$ | 43,039 | 
						  |  
				| 
						 | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 |  
				| 
						 | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 |  
				| 
						Basic weighted average shares outstanding | 
						  | 
						  | 83,222,330 | 
						  | 
						  | 83,365,218 | 
						  | 
						  | 83,432,157 | 
						  |  
				| 
						Dilutive effect of share based awards | 
						  | 
						  | 2,429,419 | 
						  | 
						  | 2,915,689 | 
						  | 
						  | 4,998,830 | 
						  |  
				| 
						 | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 |  
				| 
						Diluted weighted average shares outstanding | 
						  | 
						  | 85,651,749 | 
						  | 
						  | 86,280,907 | 
						  | 
						  | 88,430,987 | 
						  |  
				| 
						 | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 |  
				| 
						 | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 | 
						   | 
						   | 
						 |  
				| 
						Basic earnings per share | 
						  | 
						$ | 0.18 | 
						  | 
						$ | 0.32 | 
						  | 
						$ | 0.52 | 
						  |  
				| 
						Diluted earnings per share | 
						  | 
						$ | 0.18 | 
						  | 
						$ | 0.31 | 
						  | 
						$ | 0.49 | 
						  | 
			              The following have been excluded from the computation of dilutive effect of share based awards because the effect would be anti-dilutive:
		 
			                                                                                                                                                                                    
		 
			
				| 
						  | 
						  | 
						Year EndedDecember 25,
 2014
 | 
						  | 
						Year EndedDecember 31,
 2015
 | 
						  | 
						Year EndedDecember 29,
 2016
 | 
						  |  
				| 
						Stock Options | 
						  | 
						  | 1,536,690 | 
						  | 
						  | 1,856,579 | 
						  | 
						  | 2,003,651 | 
						  | 
			 
		 |