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Summary of Significant Accounting Polices - Reverse Stock Split thru Fair Value of Financial Instruments (Details) |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Oct. 31, 2013 USD ($) shares | Jun. 30, 2015 | Dec. 31, 2015 USD ($) shares | Dec. 31, 2013 USD ($) | Dec. 31, 2014 USD ($) shares | Dec. 31, 2012 USD ($)
Common Stock |  |  |  |  |  |
Reverse stock split ratio (as a percent) |  | 0.077821 |  |  |  |
Initial public offering. |  |  |  |  |  |
Issuance of preferred stock (in shares) | shares |  |  | 0 |  | 0 |
Proceeds from issuance of preferred stock |  |  | $ 12,331,000 | $ 41,422,000 |  |
Cash and Cash Equivalents |  |  |  |  |  |
Cash |  |  | 776,000 |  | $ 1,162,000 |
Money market fund |  |  | 62,004,000 |  | 13,506,000 |
Total Cash and Cash Equivalents |  |  | 62,780,000 | $ 30,474,000 | $ 14,668,000 | $ 5,434,000
Fair Value of Financial Instruments |  |  |  |  |  |
Transfers of assets or liabilities between levels |  |  | $ 0 |  |  |
Series B Convertible Preferred Stock |  |  |  |  |  |
Initial public offering. |  |  |  |  |  |
Issuance of preferred stock (in shares) | shares | 9,029,549 |  |  |  |  |
Proceeds from issuance of preferred stock | $ 0.001 |  |  |  |  |

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- Definition Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3044-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 + Details
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