Fair Value Measurements (Schedule of Financial Assets and Liabilities Measured at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 30, 2018
Financial assets:
Cash equivalents	$ 89,023	$ 93,058
Marketable securities	55,651	55,951
Forward contracts	1,216	2,889
Financial assets, fair value	145,890	151,898
Financial liabilities:
Contingent consideration related to acquisitions	0	1,575
Forward contracts	584	3,419
Liabilities, Fair Value Disclosure, Recurring	584	4,994
Level 1
Financial assets:
Cash equivalents	89,023	93,058
Financial assets, fair value	141,503	147,795
Level 2
Financial assets:
Forward contracts	1,216	2,889
Financial assets, fair value	4,387	4,103
Financial liabilities:
Forward contracts	584	3,419
Liabilities, Fair Value Disclosure, Recurring	584	3,419
Level 3
Financial liabilities:
Contingent consideration related to acquisitions	0	1,575
Liabilities, Fair Value Disclosure, Recurring	0	1,575
Certificates of deposit
Financial assets:
Marketable securities	220	219
Certificates of deposit | Level 2
Financial assets:
Marketable securities	220	219
Commercial paper
Financial assets:
Marketable securities	1,956
Commercial paper | Level 2
Financial assets:
Marketable securities	1,956
Corporate notes/bonds
Financial assets:
Marketable securities	52,480	54,737
Corporate notes/bonds | Level 1
Financial assets:
Marketable securities	52,480	54,737
U.S. government agency securities
Financial assets:
Marketable securities	995	995
U.S. government agency securities | Level 2
Financial assets:
Marketable securities	$ 995	$ 995