Fair Value Measurements Fair Value Measurement (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 27, 2014	Dec. 28, 2013	Sep. 28, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Nonrecurring	$ 0	$ 0
Assets, Fair Value Disclosure, Nonrecurring	0	0
Common Stock and Warrants [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Portion Attributable to Parent	0		0
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	$ 0	$ 6
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investment Maturity Period	12 months
Available For Sale Securities Debt Maturity Period	35 years