Organization and Significant Accounting Policies - Additional Information 1 (Detail)	12 Months Ended
	Sep. 29, 2018 USD ($) Companies	Sep. 30, 2017 USD ($)	Sep. 24, 2016 USD ($)
New Accounting Pronouncement, Early Adoption [Line Items]
Number of unconsolidated companies | Companies	9
Equity income (loss)	$ 2,800,000	$ 900,000	$ (400,000)
Investment in unconsolidated companies	18,500,000	9,200,000
Excess loss insurance that covers any health care claims	700,000
Stock-based compensation	11,602,000	11,115,000	8,356,000
Stock-based compensation after tax	8,400,000	7,000,000	5,300,000
Restricted cash	$ 10,899,000	12,645,000	$ 10,900,000
Minimum
New Accounting Pronouncement, Early Adoption [Line Items]
Owned percentage in unconsolidated entities (as percent)	13.00%
General liability and vehicle liability insurance policies	$ 250,000
Maximum
New Accounting Pronouncement, Early Adoption [Line Items]
Owned percentage in unconsolidated entities (as percent)	50.00%
General liability and vehicle liability insurance policies	$ 350,000
Other income (expense) | Purishield LLC and Ceregenin LLC
New Accounting Pronouncement, Early Adoption [Line Items]
Non-cash impairment charge		$ 16,600,000