Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Liabilities:
Kolltan acquisition contingent consideration	$ 8,750	$ 8,267
Fair value \| Level 3
Liabilities:
Kolltan acquisition contingent consideration	8,750	8,267
Fair Value Measurements. \| Level 2
Assets:
Money market funds and cash equivalents	63,946	35,066
Marketable securities	106,770	150,586
Total financial assets at fair value	170,716	185,652
Fair Value Measurements. \| Level 3
Liabilities:
Kolltan acquisition contingent consideration	8,750	8,267
Total financial liabilities at fair value	8,750	8,267
Fair Value Measurements. \| Fair value
Assets:
Money market funds and cash equivalents	63,946	35,066
Marketable securities	106,770	150,586
Total financial assets at fair value	170,716	185,652
Liabilities:
Kolltan acquisition contingent consideration	8,750	8,267
Total financial liabilities at fair value	$ 8,750	$ 8,267

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of liability recognized arising from contingent consideration in a business combination.

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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.

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Fair value of financial and nonfinancial obligations.

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Amount of investment in marketable security.

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