Fair value measurements (Details) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Marketable securities: | ||
| Available-for-sale securities, Debt Securities, Current, Total | $ 108,459 | $ 124,218 |
| Recurring basis | ||
| Marketable securities: | ||
| Corporate debt securities | 99,465 | |
| Government bonds | 6,007 | |
| Commercial paper | 2,987 | |
| Available-for-sale securities, Debt Securities, Current, Total | 108,459 | |
| Recurring basis | Level 1 | ||
| Marketable securities: | ||
| Corporate debt securities | 99,465 | |
| Government bonds | 6,007 | |
| Available-for-sale securities, Debt Securities, Current, Total | 105,472 | |
| Recurring basis | Level 2 | ||
| Marketable securities: | ||
| Commercial paper | 2,987 | |
| Available-for-sale securities, Debt Securities, Current, Total | $ 2,987 |
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- Definition Amount of investments in debt securities classified as available-for-sale, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Unsecured short-term debt instrument issued by corporations which are highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- References No definition available.
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- Definition Amount of investments in debt securities classified as trading. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Debt (bills, notes or bonds) that are issued by the government of the United States which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. No definition available.
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