Financial Instruments (Investment and Derivative Information) (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
|
| Foreign exchange contracts | ||
| Fair Value Measurements | ||
| Assets related to derivative instruments | $ 0 | |
| Liabilities related to derivative instruments | 0 | |
| Foreign exchange contracts | Other income (expense), net | Not designated as hedging instrument | ||
| Fair Value Measurements | ||
| Foreign exchange forward contracts | $ (420) | $ (548) |
| Minimum | ||
| Fair Value Measurements | ||
| Maturity period of long-term investments | 1 year | |
| Maximum | ||
| Fair Value Measurements | ||
| Maturity period of long-term investments | 2 years | |