Summary of Significant Accounting Policies - Short-term Deposits (Details) |
12 Months Ended |
|---|---|
Dec. 31, 2017 | |
| Short-term deposits | |
| Maturity term, minimum (in months) | 3 months |
| Maturity term, maximum (in months) | 12 months |
| X | ||||||||||
- Definition Maximum maturity term of short-term bank deposits. No definition available.
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| X | ||||||||||
- Definition Minimum maturity term of short-term bank deposits. No definition available.
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| X | ||||||||||
- References No definition available.
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