Summary of Income Tax Rate Before and After the Act (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2017	Dec. 30, 2016
Income Taxes [Line Items]
Earnings from Continuing Operations Before Income Taxes	$ 19,327	$ 20,904
Change in Tax Rate Due to the Act	48,600
Total Income Tax Expense	53,789	(463)
New Guidance For Accounting Standard Update | Adjustments for New Accounting Principle, Early Adoption
Income Taxes [Line Items]
Total Income Tax Expense		$ (700)
Tax Rate		(2.20%)
New Guidance For Accounting Standard Update | Adjustments for New Accounting Principle, Early Adoption | Excluding Effect Of Tax Cuts And Jobs Act
Income Taxes [Line Items]
Earnings from Continuing Operations Before Income Taxes	19,327
Income Tax Expense	5,573
Change in Tax Rate Due to the Act	(368)
Provisional Taxes Due to the Act	0
Total Income Tax Expense	$ 5,205
Tax Rate	26.90%
New Guidance For Accounting Standard Update | Adjustments for New Accounting Principle, Early Adoption | Including Effect Of Tax Cuts And Jobs Act
Income Taxes [Line Items]
Earnings from Continuing Operations Before Income Taxes	$ 19,327
Income Tax Expense	5,573
Change in Tax Rate Due to the Act	(368)
Provisional Taxes Due to the Act	48,584
Total Income Tax Expense	$ 53,789
Tax Rate	278.30%