Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 27, 2020	Jun. 30, 2021	Jun. 27, 2020
Statement Of Income And Comprehensive Income [Abstract]
Hedge loss arising during the period, tax	$ 0	$ 400,000	$ 0	$ 1,200,000
Foreign currency translation adjustment, net of tax	0	0	0	0
Unrealized gain (loss) on marketable securities, net of tax	0	0	0	0
Amortization of net actuarial pension gain included in net income, tax	$ 300,000	$ 300,000	$ 900,000	$ 800,000