Fair Value Measurements (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value Measurements
Total financial assets	$ 483,767	$ 522,454
U.S. Government securities
Fair Value Measurements
Short-term investments	157,346	157,102
Long term investments	39,584	53,336
Corporate debt securities
Fair Value Measurements
Short-term investments	104,935	74,765
Long term investments	5,122
Commercial paper
Fair Value Measurements
Short-term investments	115,925	129,528
Money market funds
Fair Value Measurements
Cash equivalents	60,855	107,723
Level 1
Fair Value Measurements
Total financial assets	257,785	318,161
Level 1 \| U.S. Government securities
Fair Value Measurements
Short-term investments	157,346	157,102
Long term investments	39,584	53,336
Level 1 \| Corporate debt securities
Fair Value Measurements
Short-term investments	0	0
Long term investments	0
Level 1 \| Commercial paper
Fair Value Measurements
Short-term investments	0	0
Level 1 \| Money market funds
Fair Value Measurements
Cash equivalents	60,855	107,723
Level 2
Fair Value Measurements
Total financial assets	225,982	204,293
Level 2 \| U.S. Government securities
Fair Value Measurements
Short-term investments	0	0
Long term investments	0	0
Level 2 \| Corporate debt securities
Fair Value Measurements
Short-term investments	104,935	74,765
Long term investments	5,122
Level 2 \| Commercial paper
Fair Value Measurements
Short-term investments	115,925	129,528
Level 2 \| Money market funds
Fair Value Measurements
Cash equivalents	0	0
Level 3
Fair Value Measurements
Total financial assets	0	0
Level 3 \| U.S. Government securities
Fair Value Measurements
Short-term investments	0	0
Long term investments	0	0
Level 3 \| Corporate debt securities
Fair Value Measurements
Short-term investments	0	0
Long term investments	0
Level 3 \| Commercial paper
Fair Value Measurements
Short-term investments	0	0
Level 3 \| Money market funds
Fair Value Measurements
Cash equivalents	$ 0	$ 0

Fair value portion of long-term investment securities.

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

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.

+ References

No definition available.

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- Definition

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

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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