Employee Compensation Plans (Details 3) (USD $)	12 Months Ended
	Sep. 29, 2012	Sep. 24, 2011	Sep. 25, 2010
Employee stock purchase plan
Compensation Plans
Average expected life	6 months	6 months	6 months
Average volatility (as a percent)	70.00%	57.00%	49.00%
Risk-free interest rate (as a percent)	0.09%	0.19%	0.22%
Weighted average fair value (in dollars per share)	$ 11.61	$ 15.97	$ 7.90
Stock options
Compensation Plans
Average expected life	6 years	6 years	6 years
Average volatility (as a percent)	69.00%	52.00%	53.00%
Risk-free interest rate (as a percent)	1.31%	2.37%	2.73%
Weighted average fair value (in dollars per share)	$ 30.10	$ 29.34	$ 15.79