Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Redeemable convertible preferred stock, par value (usd per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	8,932,851	6,875,514
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	13,067,149	10,624,486
Shares issued (in shares)	4,067,717	4,067,717
Shares outstanding (in shares)	4,067,717	4,067,717
Redeemable Convertible Preferred Stock, Series A
Shares authorized (in shares)	285,480	285,480
Shares issued (in shares)	285,480	285,480
Shares outstanding (in shares)	285,480	285,480
Liquidation value	$ 5,381,000
Redeemable Convertible Preferred Stock, Series B1
Shares authorized (in shares)	35,680	35,680
Shares issued (in shares)	35,680	35,680
Shares outstanding (in shares)	35,680	35,680
Liquidation value	$ 673,000
Redeemable Convertible Preferred Stock, Series B2
Shares authorized (in shares)	782,600	782,600
Shares issued (in shares)	782,600	782,600
Shares outstanding (in shares)	782,600	782,600
Liquidation value	$ 14,760,000
Redeemable Convertible Preferred Stock, Series C
Shares authorized (in shares)	4,115,344	4,115,344
Shares issued (in shares)	4,115,344	4,115,344
Shares outstanding (in shares)	4,115,344	4,115,344
Liquidation value	$ 113,128,000
Redeemable Convertible Preferred Stock, Series C1
Shares authorized (in shares)	1,656,410	1,656,410
Shares issued (in shares)	1,656,410	1,656,410
Shares outstanding (in shares)	1,656,410	1,656,410
Liquidation value	$ 44,354,000
Redeemable Convertible Preferred Stock, Series C2
Shares authorized (in shares)	687,474	0
Shares issued (in shares)	687,474	0
Shares outstanding (in shares)	687,474	0
Liquidation value	$ 20,345,000
Redeemable Convertible Preferred Stock, Series D
Shares authorized (in shares)	1,369,863	0
Shares issued (in shares)	1,369,863	0
Shares outstanding (in shares)	1,369,863	0
Liquidation value	$ 38,236,000

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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