The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Apr. 03, 2015	Mar. 28, 2014	Apr. 03, 2015	Mar. 28, 2014	Sep. 26, 2014
Indefinite-lived Intangible Assets [Line Items]
Amortization expense for intangible assets	$ 1,700,000us-gaap_AmortizationOfIntangibleAssets	$ 800,000us-gaap_AmortizationOfIntangibleAssets	$ 3,286,000us-gaap_AmortizationOfIntangibleAssets	$ 1,938,000us-gaap_AmortizationOfIntangibleAssets
Future amortization expense, remaining fiscal year 2015	4,900,000		4,900,000
Future amortization expense, fiscal year 2016	9,400,000		9,400,000
Future amortization expense, fiscal year 2017	5,200,000		5,200,000
Future amortization expense, fiscal year 2018	5,000,000		5,000,000
Future amortization expense, fiscal year 2019	4,900,000		4,900,000
Future amortization expense, fiscal year 2020	3,900,000		3,900,000
Future amortization expense, thereafter	2,900,000		2,900,000
In Process Research and Development
Indefinite-lived Intangible Assets [Line Items]
Research and development asset acquired fair value	$ 2,000,000		$ 2,000,000		$ 2,000,000