Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Finite-Lived Intangible Assets [Line Items]
Impairment charges	$ 50,500		$ 50,500	$ 0	$ 0
Continuing Operations
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets			27,300	$ 20,600	$ 16,600
Proton Solutions
Finite-Lived Intangible Assets [Line Items]
Impairment charges		$ 50,500	$ 50,500