Fair Value of Financial Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value of Financial Assets and Liabilities
Carrying amount of cash and cash equivalents and short term investments	$ 240,964	$ 294,855
Fair value of financial assets and liabilities
Marketable Securities	162,427	235,607
Corporate Debt Securities and Commercial Paper
Fair value of financial assets and liabilities
Marketable Securities	162,427	235,607
Recurring \| Estimated fair value
Fair value of financial assets and liabilities
Fair value of assets	231,849	283,904
Recurring \| Commercial Paper \| Estimated fair value
Fair value of financial assets and liabilities
Cash Equivalents	49,477
Recurring \| Corporate Debt Securities and Commercial Paper \| Estimated fair value
Fair value of financial assets and liabilities
Marketable Securities	162,427	235,607
Recurring \| Money Market Funds \| Estimated fair value
Fair value of financial assets and liabilities
Cash Equivalents	17,505	48,297
Recurring \| RareStone Common Stock \| Estimated fair value
Fair value of financial assets and liabilities
Other Long-term Assets	2,440
Recurring \| Level 1 \| Estimated fair value
Fair value of financial assets and liabilities
Fair value of assets	17,505	48,297
Recurring \| Level 1 \| Money Market Funds \| Estimated fair value
Fair value of financial assets and liabilities
Cash Equivalents	17,505	48,297
Recurring \| Level 2 \| Estimated fair value
Fair value of financial assets and liabilities
Fair value of assets	211,904	235,607
Recurring \| Level 2 \| Commercial Paper \| Estimated fair value
Fair value of financial assets and liabilities
Cash Equivalents	49,477
Recurring \| Level 2 \| Corporate Debt Securities and Commercial Paper \| Estimated fair value
Fair value of financial assets and liabilities
Marketable Securities	162,427	$ 235,607
Recurring \| Level 3 \| Estimated fair value
Fair value of financial assets and liabilities
Fair value of assets	2,440
Recurring \| Level 3 \| RareStone Common Stock \| Estimated fair value
Fair value of financial assets and liabilities
Other Long-term Assets	$ 2,440

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 investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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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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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Fair value portion of other assets.

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