Stockholders' Equity and Stock-Based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 28, 2013
Number of Shares (in millions)
Options outstanding at September 27, 2014	9.8
Granted	1.3	2.4	2.6
Canceled/ forfeited	(1.4)
Exercised	(3.0)
Options outstanding at September 26, 2015	6.7	9.8
Options exercisable at September 26, 2015	3.0
Options vested and expected to vest at September 26, 2015 (1)	6.6
Weighted- Average Exercise Price
Options outstanding at September 27, 2014	$ 20.59
Granted	27.68	$ 22.01	$ 20.29
Canceled/ forfeited	23.36
Exercised	18.89
Options outstanding at September 27, 2014	22.21	$ 20.59
Options exercisable at September 26, 2015	21.05
Options vested and expected to vest at September 26, 2015 (1)	$ 22.18
Weighted- Average Remaining Contractual Life (in Years)
Options outstanding at September 27, 2014	4 years 10 months 12 days	4 years 1 month 6 days
Options outstanding at September 26, 2015	4 years 10 months 12 days	4 years 1 month 6 days
Options exercisable at September 26, 2015	3 years 1 month 27 days
Options vested and expected to vest at September 26, 2015 (1)	4 years 10 months 2 days
Aggregate Intrinsic Value (in millions)
Options outstanding at September 27, 2014	$ 46.4
Exercised	42.0	$ 34.7	$ 37.6
Options outstanding at September 26, 2015	119.1	$ 46.4
Options exercisable at September 26, 2015	56.6
Options vested and expected to vest at September 26, 2015 (1)	$ 118.1