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Fair Value Measurements (Investments and Long-term Debt) (Details) - USD ($) $ in Millions | Dec. 25, 2015 | Dec. 26, 2014
--- | --- | ---
Fair Value [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | $ 919 | $ 453
Less than 1 year | 810 | 292
1 - 2 years | 9 | 45
2 - 5 years | 27 | 100
Greater than 5 years | 73 | 16
Fair Value [Member] | Certificates of Deposit and Commercial Paper [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 810 | 250
Fair Value [Member] | Corporate Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 73 | 141
Fair Value [Member] | Government securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 32 | 51
Fair Value [Member] | Auction Rate Securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 4 | 11
Fair Value [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 1 [Member] | Certificates of Deposit and Commercial Paper [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 1 [Member] | Corporate Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 1 [Member] | Government securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 1 [Member] | Auction Rate Securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 915 | 442
Long-term Debt (Including Current Maturities) | 11,340 | 11,042
Fair Value [Member] | Level 2 [Member] | Certificates of Deposit and Commercial Paper [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 810 | 250
Fair Value [Member] | Level 2 [Member] | Corporate Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 73 | 141
Fair Value [Member] | Level 2 [Member] | Government securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 32 | 51
Fair Value [Member] | Level 2 [Member] | Auction Rate Securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 3 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 4 | 11
Fair Value [Member] | Level 3 [Member] | Certificates of Deposit and Commercial Paper [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 3 [Member] | Corporate Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 3 [Member] | Government securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 0 | 0
Fair Value [Member] | Level 3 [Member] | Auction Rate Securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments at fair value | 4 | 11
Carrying Value [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Amortized cost basis of investments | 920 | 453
Carrying Value [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term Debt (Including Current Maturities) | $ 10,703 | $ 9,742

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