Fair Value Measurements (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Fair Value Measurements
Marketable securities	$ 601,989	$ 610,185
Total Assets Measured at Fair Value	860,410	825,908
Fair value assets Level1 To Level 2	0
Fair value assets Level2 To Level 1	0
Fair value assets transfers into Level3	0
Fair value assets transfers out of Level3	0
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value Measurements
Marketable securities	601,989	610,185
Cash and cash equivalents	258,421	215,723
Total Assets Measured at Fair Value	860,410	825,908
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value Measurement [Member] \| Corporate Bond Securities [Member]
Fair Value Measurements
Marketable securities	54,673	117,928
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value Measurement [Member] \| Commercial Paper [Member]
Fair Value Measurements
Marketable securities	547,316	492,257
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value Measurements
Cash and cash equivalents	258,421	215,723
Total Assets Measured at Fair Value	258,421	215,723
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value Measurements
Marketable securities	601,989	610,185
Total Assets Measured at Fair Value	601,989	610,185
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Bond Securities [Member]
Fair Value Measurements
Marketable securities	54,673	117,928
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commercial Paper [Member]
Fair Value Measurements
Marketable securities	$ 547,316	$ 492,257

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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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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), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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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.

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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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-Publisher FASB
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-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

+ 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 (c)(3)
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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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