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Fair Value Measurements (Details 1) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value |  |
Cash and Cash Equivalents | $ 15,044 | $ 61,661
Short-term Investments | 194,645 | 249,127
Total Cash and Cash Equivalents and Investments | 209,689 | 310,788
Fair Value, Level 1 |  |
Fair Value |  |
Cash and Cash Equivalents | 15,044 | 61,661
Short-term Investments | 174,082 | 222,148
Total Cash and Cash Equivalents and Investments | 189,126 | 283,809
Fair Value, Level 2 |  |
Fair Value |  |
Cash and Cash Equivalents | 0 | 0
Short-term Investments | 20,563 | 26,979
Total Cash and Cash Equivalents and Investments | 20,563 | 26,979
Fair Value, Level 3 |  |
Fair Value |  |
Cash and Cash Equivalents | 0 | 0
Short-term Investments | 0 | 0
Total Cash and Cash Equivalents and Investments | $ 0 | $ 0

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes 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. + References No definition available. + Details
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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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