Net Loss Per Share - Antidilutive (Details) - shares	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	17,429,417	18,848,933
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	2,929,095	5,122,470
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	13,806,088	12,791,608
ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	194,622	194,366
Stock-settled bonus shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (shares)	499,612	740,489