Employee Stock Plans - Fair Value with Weighted Average Assumptions (Detail) (USD $)	12 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 28, 2012
Employee Stock Option plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	4 years 1 month 17 days	4 years 9 months 4 days	4 years 7 months 21 days
Risk-free interest rate	1.20%	0.60%	0.80%
Expected volatility	24.60%	32.20%	36.90%
Expected dividend	0.00%	0.00%	0.00%
Weighted average fair value at grant date	$ 18.24	$ 19.73	$ 18.75
Employee Stock Purchase Plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months
Risk-free interest rate	0.10%	0.10%	0.10%
Expected volatility	12.80%	16.50%	19.30%
Expected dividend	0.00%	0.00%	0.00%
Weighted average fair value at grant date	$ 14.20	$ 12.95	$ 12.17