Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 28, 2012
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense for intangible assets	$ 4,779,000	$ 4,332,000	$ 4,879,000
Future amortization expense, fiscal year 2015	8,700,000
Future amortization expense, fiscal year 2016	8,100,000
Future amortization expense, fiscal year 2017	5,200,000
Future amortization expense, fiscal year 2018	5,000,000
Future amortization expense, fiscal year 2019	5,000,000
Future amortization expense, thereafter	6,900,000
Research and development asset acquired fair value	$ 2,000,000