Fair Value Measurements (Schedule of Financial Assets and Liabilities Measured at Fair Value) (Details) - USD ($) $ in Thousands	Mar. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Financial assets:
Cash equivalents	$ 97,748	$ 93,058
Marketable securities	56,415	55,951
Forward contracts	3,900	2,889
Financial assets, fair value	158,063	151,898
Financial liabilities:
Contingent consideration related to acquisitions	0	1,575
Forward contracts	3,014	3,419
Financial liabilities, fair value	3,014	4,994
Level 1
Financial assets:
Cash equivalents	97,748	93,058
Financial assets, fair value	151,187	147,795
Level 2
Financial assets:
Forward contracts	3,900	2,889
Financial assets, fair value	6,876	4,103
Financial liabilities:
Forward contracts	3,014	3,419
Financial liabilities, fair value	3,014	3,419
Level 3
Financial liabilities:
Contingent consideration related to acquisitions	0	1,575	$ 6,743	$ 8,400
Financial liabilities, fair value	0	1,575
Certificates of deposit
Financial assets:
Marketable securities		219
Certificates of deposit | Level 2
Financial assets:
Marketable securities		219
Commercial paper
Financial assets:
Marketable securities	1,975
Commercial paper | Level 2
Financial assets:
Marketable securities	1,975
Corporate notes/bonds
Financial assets:
Marketable securities	53,439	54,737
Corporate notes/bonds | Level 1
Financial assets:
Marketable securities	53,439	54,737
U.S. government agency securities
Financial assets:
Marketable securities	1,001	995
U.S. government agency securities | Level 2
Financial assets:
Marketable securities	$ 1,001	$ 995