Redeemable Convertible Preferred Stock and Stockholders' Deficit - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Temporary Equity And Stockholder's Equity [Abstract]
Redeemable convertible preferred stock outstanding	55,422,002	55,422,002	55,422,002
Stock options issued and outstanding	13,782,401	13,291,684
Shares available for future equity grants	4,148,810	4,941,504
Total	73,353,213	73,655,190