CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (26,021)	$ (15,578)	$ 139,172	$ 101,946
Other comprehensive income:
Amortization of net actuarial losses and prior service credits into earnings	593	541	1,779	1,623
Recognition in earnings of net actuarial loss for pension settlement	142	900	712	900
Other comprehensive income	735	1,441	2,491	2,523
Total comprehensive (loss) income	$ (25,286)	$ (14,137)	$ 141,663	$ 104,469