Significant Accounting Policies - Principles of Consolidation (Details)	12 Months Ended
	Dec. 27, 2015 item	Dec. 28, 2014 item	Dec. 29, 2013 USD ($) item
Significant accounting policies
Period in arrears to consolidate operations			1 month
Number of weeks in fiscal year | item	52	52	52
Minimum
Significant accounting policies
Amortization term of equipment incentives	2 years
Maximum
Significant accounting policies
Amortization term of equipment incentives	3 years
International
Significant accounting policies
Incremental change in revenues due to change in consolidation policy			$ 2,100,000
Incremental change in loss before income taxes due to change in consolidation policy			$ 215,000