Fair Value Measurements -Schedule of estimated fair value for the warrant liabilities measured using significant unobservable inputs (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Beginning balance	$ 8,846	$ 71,881
Exercise of preferred stock warrants	(1,111)	(24)
Expiration of common stock warrants	(5,018)	0
Change in fair value of common stock warrant	0	(64,628)
Change in fair value of preferred stock warrants	(2,717)	1,617
Ending balance	$ 0	$ 8,846

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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 (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant