Organization and Summary of Significant Accounting Policies - Narrative - Derivatives (Details) - USD ($) $ in Millions |
Dec. 31, 2017 |
Jan. 01, 2017 |
|---|---|---|
| Foreign exchange forward [Member] | Not designated as hedging instrument [Member] | ||
| Derivative Instruments, Gain (Loss) [Line Items] | ||
| Notional amount of outstanding forward contracts | $ 88 | $ 69 |