Commitments and Contingencies Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2016	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Outstanding letters of credit	$ 4.6	$ 2.0
Employee stock purchase plan
Loss Contingency [Abstract]
Common stock issued under the ESPP, subject to rescission rights (in shares)	90,358
Common Stock Price 1 | Employee stock purchase plan
Loss Contingency [Abstract]
Common stock issued under the ESPP, subject to rescission rights (in shares)	43,968
Share price (in dollars per share)	$ 8.00
Common Stock Price 2 | Employee stock purchase plan
Loss Contingency [Abstract]
Common stock issued under the ESPP, subject to rescission rights (in shares)	46,390
Share price (in dollars per share)	$ 8.02
Employee Stock Purchase Plan, Rescission Rights | Employee stock purchase plan
Loss Contingency [Abstract]
Estimate of aggregate payments	$ 0.8