Convertible Preferred Stock Warrants and Common Stock Warrants - Schedule of Warrants Issued and Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding		468,278		680,027	680,027
Fair value of warrants issued and outstanding			$ 300	$ 1,875	$ 1,351
The June 2012 Series B-1 convertible preferred stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding				25,568	25,568
Fair value of warrants issued and outstanding				$ 303	$ 142
Issuance Date		2012-06
Price per Share		$ 5.8667
Expiration Date		2022-06
The July 2012 Series B-1 convertible preferred stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding				167,428	167,428
Fair value of warrants issued and outstanding				$ 263	$ 124
Issuance Date		2012-07
Price per Share		$ 5.8667
Expiration Date		2019-07
The August 2012 Series B-1 convertible preferred stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding				145,801	145,801
Fair value of warrants issued and outstanding				$ 46	$ 22
Issuance Date		2012-08
Price per Share		$ 5.8667
Expiration Date		2019-08
The November 2012 Series B-1 convertible preferred stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding				10,517	10,517
Fair value of warrants issued and outstanding				$ 19	$ 9
Issuance Date		2012-11
Price per Share		$ 5.8667
Expiration Date		2022-11
The February 2014 Series B-1 convertible preferred stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding				156,851	156,851
Fair value of warrants issued and outstanding				$ 929	$ 907
Issuance Date		2014-02
Price per Share		$ 0.1700
Expiration Date		2021-02
The September 2015 Series B-1 convertible preferred stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding				173,862	173,862
Fair value of warrants issued and outstanding				$ 315	$ 147
Issuance Date		2015-09
Price per Share		$ 5.8667
Expiration Date		2025-09
The July 2012 Common stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding		165,925
Issuance Date		2012-07
Price per Share		$ 5.8667
Expiration Date		2019-07
The August 2012 Common stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding		61,502
Issuance Date		2012-08
Price per Share		$ 5.8667
Expiration Date		2019-08
The February 2014 Common stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding		156,851
Issuance Date		2014-02
Price per Share		$ 0.1700
Expiration Date		2021-02
The June 2017 Common stock warrant
Class Of Warrant Or Right [Line Items]
Shares of warrants issued and outstanding	[1]	84,000
Issuance Date	[1]	2017-06
Price per Share	[1]	$ 13.2000
Expiration Date	[1]	2020-06

[1] This warrant was issued to the Company’s lead underwriter in connection with the IPO