Net Loss Per Share - Antidilutive (Details) - shares	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	16,888,351	18,512,970	22,556,542
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	2,898,977	4,496,557	7,738,496
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	12,639,066	12,303,913	12,906,030
ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	478,917	478,026	726,643
Stock-settled bonus shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	871,391	1,234,474	1,185,373