CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 25, 2017	Mar. 31, 2018	Mar. 25, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 106,787	$ 83,812	$ 143,955	$ 118,301
Other comprehensive income:
Net unrealized (losses) on cash flow hedges	0	(5)	0	(10)
Reclassification of realized losses on cash flow hedges into earnings	0	15	0	215
Amortization of net actuarial losses and prior service credits into earnings	757	1,203	1,514	2,406
Other comprehensive income	757	1,213	1,514	2,611
Total comprehensive income	$ 107,544	$ 85,025	$ 145,469	$ 120,912