Fair Value Measurements - Schedule of Fair Value of Investment Assets (Details) - USD ($) $ in Millions	Jun. 26, 2015	Dec. 26, 2014
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized cost basis of investments	$ 777	$ 453
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	777	453
Certificates of Deposit and Commercial Paper | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	670	250
Corporate Bonds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	71	141
Government Securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	32	51
Auction Rate Securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	4	11
Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	773	442
Level 2 | Certificates of Deposit and Commercial Paper | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	670	250
Level 2 | Corporate Bonds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	71	141
Level 2 | Government Securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	32	51
Level 2 | Auction Rate Securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	0	0
Level 3 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	4	11
Level 3 | Certificates of Deposit and Commercial Paper | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	0	0
Level 3 | Corporate Bonds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	0	0
Level 3 | Government Securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	0	0
Level 3 | Auction Rate Securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments at fair value	$ 4	$ 11