Significant Accounting Policies - Basis of Presentation and Principles of Consolidation (Details)	9 Months Ended	12 Months Ended
	Sep. 29, 2018	Dec. 30, 2017
Significant Accounting Policies
Length of fiscal year	364 days	364 days
Number of days in each fiscal quarter for 52-week fiscal year	91 days
Low end of range
Significant Accounting Policies
Length of fiscal year	364 days
High end of range
Significant Accounting Policies
Length of fiscal year	371 days