Employee Benefit Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Sep. 30, 2015	Oct. 31, 2014	Sep. 30, 2012	Sep. 30, 2009	Mar. 31, 2017
Employee Benefit Plans
Shares of common stock available for grant					2,443,000
Number of Options
Options outstanding at the end of the period (in shares)					3,776,000
Number of Shares
RSUs outstanding at the end of the period (in shares)					232,000
Stock options
Number of Options
Options outstanding at the beginning of the period (in shares)					3,309,000
Granted (in shares)					905,000
Exercised (in shares)					(388,000)
Forfeited (in shares)					(37,000)
Expired (in shares)					(13,000)
Options outstanding at the end of the period (in shares)					3,776,000
Options exercisable at the end of the period (in shares)					1,396,000
Vested and expected to vest at the end of the period (in shares)					3,406,000
Weighted Average Exercise Price Per Share
Options outstanding at the beginning of the period (in dollars per share)					$ 2.07
Granted (in dollars per share)					4.81
Exercised (in dollars per share)					1.72
Forfeited (in dollars per share)					2.25
Expired (in dollars per share)					2.06
Options outstanding at the end of the period (in dollars per share)					2.76
Options exercisable at the end of the period (in dollars per share)					1.99
Vested and expected to vest at the end of the period (in dollars per share)					$ 2.66
Weighted Average Remaining Contractual Life
Options outstanding at the end of the period					8 years
Options exercisable at the end of the period					6 years 4 months 24 days
Vested and expected to vest at the end of the period					7 years 9 months 18 days
Aggregate Intrinsic Value
Options outstanding at the end of the period (in dollars)					$ 10,115
Options exercisable at the end of the period (in dollars)					4,822
Vested and expected to vest at the end of the period (in dollars)					$ 9,483
Stock options | Change in Control
Number of Options
Options exercisable at the end of the period pursuant to a change-in-control (in shares)					3,776,000
Weighted Average Exercise Price Per Share
Options exercisable at the end of the period (in dollars per share)					$ 2.76
Weighted Average Remaining Contractual Life
Options exercisable at the end of the period					8 years
Aggregate Intrinsic Value
Options exercisable at the end of the period pursuant to a change-in-control (in dollars)					$ 10,115
Restricted stock units
Number of Shares
RSUs outstanding at the beginning of the period (in shares)					173,000
Granted (in shares)					141,000
Vested (in shares)					(68,000)
Forfeited (in shares)					(14,000)
RSUs outstanding at the end of the period (in shares)					232,000
Expected to vest at the end of the period (in shares)					180,000
Weighted Average Price Per Share
RSUs outstanding at the beginning of the period (in dollars per share)					$ 2.00
Granted (in dollars per share)					4.98
Vested (in dollars per share)					1.93
Forfeited (in dollars per share)					2.05
RSUs outstanding at the end of the period (in dollars per share)					3.84
Expected to vest at the end of the period (in dollars per share)					$ 3.83
Weighted Average Remaining Life
RSUs outstanding at the end of the period					1 year 9 months 18 days
Expected to vest at the end of the period					1 year 8 months 12 days
Aggregate Intrinsic Value
RSUs outstanding at the end of the period (in dollars)					$ 477
Expected to vest at the end of the period (in dollars)					$ 377
Restricted stock units | Change in Control
Number of Shares
Common stock issuable (for RSUs) at the end of the period upon a change-in-control (in shares)					232,000
Weighted Average Price Per Share
Vested (in dollars per share)					$ 3.84
Weighted Average Remaining Life
RSUs outstanding at the end of the period					1 year 9 months 18 days
Aggregate Intrinsic Value
Common stock issuable (for RSUs) at the end of the period upon a change-in-control (in dollars)					$ 477
2007 Plan
Employee Benefit Plans
Increase in number of shares of common stock authorized and reserved for issuance under the plan	1,000,000	1,500,000	800,000	800,000
Stock options authorized under the plan (in shares)	4,950,000	3,950,000	2,450,000	1,650,000
2007 Plan | Stock options
Employee Benefit Plans
Vesting percentage					25.00%
Vesting period					4 years
Number of Options
Options outstanding at the end of the period (in shares)					2,942,000
2007 Plan | Stock options | Maximum
Employee Benefit Plans
Expiration term					10 years
2007 Plan | Restricted stock units
Employee Benefit Plans
Vesting percentage					25.00%
Vesting period					4 years
Aggregate Intrinsic Value
Number of shares of common stock receivable upon vesting of each RSU					1
Number of Shares
RSUs outstanding at the end of the period (in shares)					93,000
2016 Plan
Employee Benefit Plans
Shares of common stock available for grant					2,400,000
2016 Plan | Stock options
Employee Benefit Plans
Vesting percentage					25.00%
Vesting period					4 years
Number of Options
Options outstanding at the end of the period (in shares)					835,000
2016 Plan | Stock options | Maximum
Employee Benefit Plans
Expiration term					10 years
2016 Plan | Restricted stock units
Number of Shares
RSUs outstanding at the end of the period (in shares)					139,000
2016 Plan | Restricted stock units | Minimum
Employee Benefit Plans
Vesting period					1 year
2016 Plan | Restricted stock units | Maximum
Employee Benefit Plans
Vesting period					4 years