Net Income (loss) per Share Attributable to Common Stock - Summary of Anti-dilutive Stock Equivalents (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	179,712	69,204,403	12,785,998	69,204,403
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	0	55,422,002	0	55,422,002
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	0	13,782,401	10,775,812	13,782,401
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	179,712	0	2,010,186	0