Marketable Securities (Schedule of Available-for-sale Marketable Securities by Contractual Maturity Date) (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, amortized cost	$ 25,544	$ 25,792
Due in one year or less, fair value	25,430	25,670
Due after one year through three years, amortized cost	30,506	30,572
Due after one year through three years, fair value	30,221	30,281
Amortized cost	56,050	56,364
Fair value	$ 55,651	$ 55,951