Investments - Continuous Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses	$ (12)	$ (2)
Fair Value	128,502	16,294
U.S. Treasury
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses	(6)	0
Fair Value	65,298	0
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses	(4)	(1)
Fair Value	47,629	13,422
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses	(2)	(1)
Fair Value	$ 15,575	$ 2,872

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922890-210455

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant