Stockholders' Equity - 2006 Plan Activity (Details) - Employee and director options - $ / shares	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017
Stock option activity
Options outstanding at the beginning of the period (in shares)	1,704,973	1,708,487
Options granted (in shares)	531,300	232,845
Options exercised (in shares)	0	(12,421)
Options cancelled (in shares)	(225,516)	(223,938)
Options outstanding at the end of the period (in shares)	2,010,757	1,704,973
Options exercisable at the end of the period (in shares)	1,109,171
Weighted-Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 13.43	$ 13.91
Options granted (in dollars per share)	4.65	9.18
Options exercised (in dollars per share)	0.00	7.41
Options cancelled (in dollars per share)	12.39	13.00
Options outstanding at the end of the period (in dollars per share)	11.23	$ 13.43
Options exercisable at the end of the period (in dollars per share)	$ 15.30