Stockholder's Equity (Deficit) - Summary of Assumptions Used to Value Convertible Preferred Stock Warrants (Details) - Convertible Preferred Stock Warrants	Dec. 31, 2017	Dec. 31, 2016
Minimum \| Expected term (in years)
Class Of Warrant Or Right [Line Items]
Fair value assumptions term	3 years	3 years 2 months 12 days
Minimum \| Risk-free interest rate
Class Of Warrant Or Right [Line Items]
Fair value assumptions	1.5	0.7
Minimum \| Expected volatility
Class Of Warrant Or Right [Line Items]
Fair value assumptions	44	46
Maximum \| Expected term (in years)
Class Of Warrant Or Right [Line Items]
Fair value assumptions term	9 years 8 months 12 days	3 years 10 months 24 days
Maximum \| Risk-free interest rate
Class Of Warrant Or Right [Line Items]
Fair value assumptions	2.3	1.6
Maximum \| Expected volatility
Class Of Warrant Or Right [Line Items]
Fair value assumptions	51	48

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- Definition

Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

+ 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 (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Period between issuance and expiration of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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