Commitments and Contingencies - Contingencies (Details) - Employee stock purchase plan $ / shares in Units, $ in Millions	6 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Loss Contingency [Abstract]
Common stock issued under the ESPP, subject to rescission rights (in shares) | shares	37,710
Share price (in dollars per share) | $ / shares	$ 8.02
Employee Stock Purchase Plan, Rescission Rights
Loss Contingency [Abstract]
Estimate of aggregate payments | $	$ 0.3