Acquired Intangible Assets - Additional Information (Details) - USD ($) $ in Billions	12 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 26, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense related to acquired intangible assets	$ 1.2	$ 1.5	$ 1.3
Weighted-average amortization period for acquired intangible assets	3 years 5 months