Nature of Business and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 25, 2016

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The fair value of each option grant is estimated on the date of grant using the Black-Scholes-Merton option valuation model with the following assumptions:



	Stock Options
	December 25, 2016	December 27, 2015	December 28, 2014
Expected dividend yield	0.0%	0.0%	0.0%
Expected stock price volatility	34.1%	34.3%	35.7%
Risk-free interest rate	1.4%	1.4%	1.7%
Expected life of options	4.7	5	5

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]



	Employee Stock Purchase Plan
	December 25, 2016				December 27, 2015				December 28, 2014
Expected dividend yield		0.0	%			0.0	%			0.0	%
Expected stock price volatility	29.3	—		35.3%	31.1	—		37.9%	45.5	—		45.9%
Risk-free interest rate		0.50	%			0.23	%			0.05	%
Expected life of options		0.5				0.5				0.5