Financial Instruments (Narrative) (Details) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2018 |
Dec. 30, 2017 |
|
| Schedule of Investments [Line Items] | ||
| Carrying value of cost method investments | $ 3 | $ 3 |
| Foreign Currency Forward Contracts | ||
| Schedule of Investments [Line Items] | ||
| Contract maturity period | 12 months | |
| Maximum length of time hedged in foreign currency cash flow hedges | 12 months | |
| Cash Flow Hedging | Foreign Currency Forward Contracts | ||
| Schedule of Investments [Line Items] | ||
| Derivative, notional amount | $ 355 | 300 |
| Level 1 | Government money market funds | ||
| Schedule of Investments [Line Items] | ||
| Investment in money market fund and bank guarantee | 5 | 2 |
| Level 1 | Bank guarantee | ||
| Schedule of Investments [Line Items] | ||
| Investment in money market fund and bank guarantee | 3 | |
| Level 1 | Mutual funds | ||
| Schedule of Investments [Line Items] | ||
| Restricted investments | $ 20 | $ 18 |