Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2018	Sep. 30, 2017
Stockholders' equity
Shares reserved for future issuance (in shares)	47,397,361	4,218,016
Common stock warrants
Stockholders' equity
Shares reserved for future issuance (in shares)	42,024,566	24,566
Stock options
Stockholders' equity
Shares reserved for future issuance (in shares)	4,612,684	3,669,791
Employee Stock Purchase Plan
Stockholders' equity
Shares reserved for future issuance (in shares)	760,111	523,659