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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-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

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)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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- Definition

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

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Fair Value Measurements - (Details) - USD ($)	3 Months Ended		9 Months Ended
Fair Value Measurements - (Details) - USD ($)	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Fair value of the Company's financial assets
Marketable Securities	$ 198,672,000		$ 198,672,000		$ 250,676,000
Assets transferred into level 3	0	$ 0	0	$ 0
Assets transferred out of level 3	0	$ 0	0	$ 0
Fair Value
Fair value of the Company's financial assets
Total financial assets	219,943,000		219,943,000		261,831,000
Fair Value \| Quoted Prices in Active Markets (Level 1)
Fair value of the Company's financial assets
Total financial assets	21,271,000		21,271,000		11,155,000
Fair Value \| Significant Other Observable Inputs (Level 2)
Fair value of the Company's financial assets
Total financial assets	198,672,000		198,672,000		250,676,000
Money market funds (cash equivalents) \| Fair Value
Fair value of the Company's financial assets
Money market funds (cash equivalents)	21,271,000		21,271,000		11,155,000
Money market funds (cash equivalents) \| Fair Value \| Quoted Prices in Active Markets (Level 1)
Fair value of the Company's financial assets
Money market funds (cash equivalents)	21,271,000		21,271,000		11,155,000
Corporate bonds \| Fair Value
Fair value of the Company's financial assets
Marketable Securities	198,672,000		198,672,000		243,679,000
Corporate bonds \| Fair Value \| Significant Other Observable Inputs (Level 2)
Fair value of the Company's financial assets
Marketable Securities	$ 198,672,000		$ 198,672,000		243,679,000
Commercial Paper \| Fair Value
Fair value of the Company's financial assets
Marketable Securities					6,997,000
Commercial Paper \| Fair Value \| Significant Other Observable Inputs (Level 2)
Fair value of the Company's financial assets
Marketable Securities					$ 6,997,000