Nature of the Business and Basis of Presentation - Liquidity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Cash, cash equivalents, restricted cash and marketable securities	$ 149,200
Restricted cash and cash equivalents	1,400
Accumulated deficit	429,226	$ 404,629
Russian subsidiary
Cash and Cash Equivalents [Line Items]
Cash maintained in Russian bank accounts	$ 300

Cash, Cash Equivalents, Restricted Cash And Restricted Cash Equivalents And Debt Securities, Available-For-Sale

No definition available.

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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. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, 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.

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- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

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