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Common Stock - Schedule of Common Stock Reserved for Issuance (Detail) - shares | Sep. 30, 2016 | Dec. 31, 2015
--- | --- | ---
Class of Stock [Line Items] |  |
Total | 2,565,984 | 6,579,361
Redeemable Convertible Preferred Stock [Member] |  |
Class of Stock [Line Items] |  |
Total |  | 5,323,103
Options Issued and Outstanding [Member] |  |
Class of Stock [Line Items] |  |
Total | 1,496,156 | 833,178
Redeemable Convertible Preferred Stock Warrant Liability [Member] |  |
Class of Stock [Line Items] |  |
Total |  | 275,861
Options Available for Future Grants [Member] |  |
Class of Stock [Line Items] |  |
Total | 1,069,828 | 147,219

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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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