Schedule of Amounts Recognized in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 28, 2018	Sep. 29, 2017
Amount Recognized in the Consolidated Balance Sheet
Non-current liability	$ (57,755)	$ (66,981)
Amounts Recognized in Accumulated Other Comprehensive Income
Ending balance	55,817	81,782
Pension Plan
Amount Recognized in the Consolidated Balance Sheet
Non-current asset	22,776	4,267
Current liability	(2,795)	(1,840)
Non-current liability	(45,567)	(54,108)
Net amount recognized	(25,586)	(51,681)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial loss (gain)	52,659	78,713
Prior service cost	3,040	2,593
Ending balance	55,699	81,306
Other Postretirement Benefit Plan
Amount Recognized in the Consolidated Balance Sheet
Non-current asset	0	0
Current liability	(732)	(669)
Non-current liability	(12,188)	(12,873)
Net amount recognized	(12,920)	(13,542)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial loss (gain)	118	476
Prior service cost	0	0
Ending balance	$ 118	$ 476

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