Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Sep. 26, 2014	Dec. 27, 2013
Fair Value
Fair Value, by Balance Sheet Grouping
Investments	$ 767	$ 668
Fair Value | Less than 1 year
Fair Value, by Balance Sheet Grouping
Investments	575	487
Fair Value | 1 - 2 years
Fair Value, by Balance Sheet Grouping
Investments	55	58
Fair Value | 2 - 5 years
Fair Value, by Balance Sheet Grouping
Investments	123	105
Fair Value | Greater than 5 years
Fair Value, by Balance Sheet Grouping
Investments	14	18
Fair Value | Certificates of Deposit and Commercial Paper
Fair Value, by Balance Sheet Grouping
Investments	565	472
Fair Value | Corporate Bonds
Fair Value, by Balance Sheet Grouping
Investments	143	132
Fair Value | Government Securities
Fair Value, by Balance Sheet Grouping
Investments	48	49
Fair Value | Auction Rate Securities
Fair Value, by Balance Sheet Grouping
Investments	11	15
Fair Value | Level 1
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 1 | Certificates of Deposit and Commercial Paper
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 1 | Corporate Bonds
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 1 | Government Securities
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 1 | Auction Rate Securities
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 2
Fair Value, by Balance Sheet Grouping
Investments	756	653
Long-term Debt (Including Current Maturities)	10,715	10,354
Fair Value | Level 2 | Certificates of Deposit and Commercial Paper
Fair Value, by Balance Sheet Grouping
Investments	565	472
Fair Value | Level 2 | Corporate Bonds
Fair Value, by Balance Sheet Grouping
Investments	143	132
Fair Value | Level 2 | Government Securities
Fair Value, by Balance Sheet Grouping
Investments	48	49
Fair Value | Level 2 | Auction Rate Securities
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 3
Fair Value, by Balance Sheet Grouping
Investments	11	15
Fair Value | Level 3 | Certificates of Deposit and Commercial Paper
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 3 | Corporate Bonds
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 3 | Government Securities
Fair Value, by Balance Sheet Grouping
Investments	0	0
Fair Value | Level 3 | Auction Rate Securities
Fair Value, by Balance Sheet Grouping
Investments	11	15
Carrying Value
Fair Value, by Balance Sheet Grouping
Amortized cost basis of investments	767	668
Carrying Value | Level 2
Fair Value, by Balance Sheet Grouping
Long-term Debt (Including Current Maturities)	$ 9,617	$ 9,555