Organization and Business Activities - Liquidity (Details) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($) shares
Liquidity
Cash, cash equivalents and short-term investments	$ 89,600
Proceeds from sale of ordinary shares	$ 19,388
At-the-market offering
Liquidity
Number of shares issued \| shares	3,517,511
Proceeds from sale of ordinary shares	$ 19,400
Proceeds from sale of stock, net of commissions	18,900
Cantor Fitzgerald and Co. \| Sales Agreement
Liquidity
Aggregate gross proceeds	$ 50,000

Represents aggregate offering price pursuant to an effective shelf registration statement.

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- Definition

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal 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. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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Cash received on stock transaction after deduction of issuance costs.

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Number of new stock issued during the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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