Financial Instruments (Narrative) (Details) - Level 1 - USD ($) $ in Millions |
Sep. 24, 2016 |
Dec. 26, 2015 |
|---|---|---|
| Money Market Funds | ||
| Schedule of Investments [Line Items] | ||
| Available-for-sale investments used as collateral | $ 3 | $ 1 |
| Mutual Funds | ||
| Schedule of Investments [Line Items] | ||
| Restricted investments | $ 14 | $ 15 |