Stockholders' Equity and Stock-Based Compensation - Assumptions to Value Stock Options (Detail) - USD ($)	12 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 28, 2013
Assumptions:
Risk-free interest rates	1.70%	1.20%	0.50%
Expected life (in years)	5 years 4 months 6 days	4 years 4 months 24 days	4 years 4 months 24 days
Expected volatility	38.60%	41.40%	43.70%
Dividend yield	$ 0	$ 0	$ 0
Employee stock purchase plan [Member]
Assumptions:
Risk-free interest rates	0.10%	0.08%	0.11%
Expected life (in years)	6 months	6 months	6 months
Expected volatility	27.40%	30.00%	32.00%
Dividend yield	$ 0	$ 0	$ 0