Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Grants Outside of 2000 and 2017 Plans and Stockholder Rights Plan (Details)

Stockholders' Equity - Grants Outside of 2000 and 2017 Plans and Stockholder Rights Plan (Details) $ / shares in Units, $ in Thousands								3 Months Ended	12 Months Ended
	Oct. 27, 2017 USD ($) $ / shares	Oct. 21, 2016 USD ($)	Oct. 18, 2016 $ / shares shares	May 06, 2016 Vote $ / shares	Apr. 22, 2016 USD ($)	Apr. 19, 2016 $ / shares shares	Aug. 28, 2015 USD ($)	Mar. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares shares	Oct. 26, 2017 $ / shares shares	Aug. 31, 2017 $ / shares
Stockholder Rights Plan
Preferred stock, par value (in dollars per share) \| $ / shares								$ 0.001	$ 0.001	$ 0.001
At-the-market Offering Program and Underwritten Offering of Common Stock
Net proceeds from sale of the common stock, after deducting fees and other offering expenses (in dollars) \| $					$ 13,100			$ 5,300	$ 11,900
Common stock, par value (in dollars per share) \| $ / shares	$ 0.001							$ 0.001	$ 0.001	$ 0.001
Reduction of warrants to purchase common stock (as a percent)	19.00%
Number of common stock shares available to accredited investors			3,600,000
Share price of common stock sold (in dollars per share) \| $ / shares			$ 1.20
Loss on adjustment of exercise price \| $									$ 741	$ 421
Net proceeds from offering of common stock and warrants \| $		$ 6,800							$ 13,581	$ 20,188
Number of common stock shares available in public offering						2,700,000
Number of warrants or shares of common stock to be sold to purchase common stock						2
Common stock sold (in shares)								6,700,000	16,000,000
Common stock commissions paid \| $								$ 200	$ 300
Total shares of common stock sold pursuant to the at-the-market offering program								23,300,000	23,300,000
Total net proceeds from sale of common stock \| $								$ 24,600	$ 24,600
Total common stock commissions paid \| $								700	700
Common stock available for issuance \| $								$ 4,100	4,100
Series A Warrants
At-the-market Offering Program and Underwritten Offering of Common Stock
Number of shares of common stock that could be purchased with warrants						4,100,000					1,928,750
Exercise price (in dollars per share) \| $ / shares			1.34			$ 3.50					$ 0.90	$ 0.60
Net proceeds from sale of the common stock, after deducting fees and other offering expenses (in dollars) \| $	$ 1,700
Loss on adjustment of exercise price \| $									$ 700
Number of warrants or shares of common stock to be sold to purchase common stock						1
Number of shares of common stock purchased with each warrant						1
Length of time from issue date until warrants are exercisable						6 months
Length of time from exercise date until warrants expire						5 years
Outstanding warrants (in shares)								8,478,750	8,478,750
Series B Warrants
At-the-market Offering Program and Underwritten Offering of Common Stock
Number of shares of common stock that could be purchased with warrants						5,500,000
Exercise price (in dollars per share) \| $ / shares			1.20			$ 3.48
Exercise price pre-funded at closing (in dollars per share) \| $ / shares			1.19
Exercise price, payable upon exercise (in dollars per share) \| $ / shares			$ 0.01
Number of warrants or shares of common stock to be sold to purchase common stock						2
Number of shares of common stock purchased with each warrant						1
Length of time from exercise date until warrants expire						9 months
Outstanding warrants (in shares)								0	0
Minimum \| Series B Warrants
At-the-market Offering Program and Underwritten Offering of Common Stock
Number of shares of common stock that could be purchased with warrants			2,700,000
Maximum
At-the-market Offering Program and Underwritten Offering of Common Stock
Aggregate offering price for at-the-market offering program \| $							$ 30,000
Maximum \| Series A Warrants
At-the-market Offering Program and Underwritten Offering of Common Stock
Number of shares of common stock that could be purchased with warrants			6,300,000
Stock options
Class of Stock [Line Items]
Options outstanding (in shares)								212,392	212,392	314,537
Portion vesting one year after the issuance date (as a percent)									25.00%
Portion vesting on first day of each month after one year from the issuance date (as a percent)									2.083%
Expiration Term									10 years
Vesting period									4 years
Stock options \| Grants outside of 2000 and 2017 Plans
Class of Stock [Line Items]
Options outstanding (in shares)										88,930
Portion vesting one year after the issuance date (as a percent)									25.00%
Portion vesting on first day of each month after one year from the issuance date (as a percent)									2.083%
Expiration Term									10 years
Vesting period									4 years
Restricted stock units
Class of Stock [Line Items]
Restricted stock units outstanding (in shares)								2,011,611	2,011,611	316,709
Restricted stock units \| Grants outside of 2000 and 2017 Plans
Class of Stock [Line Items]
Restricted stock units outstanding (in shares)										14,820
Series B Junior Participating Preferred Stock
Stockholder Rights Plan
Preferred share purchase right ratio				1
Preferred stock conversion basis				0.001
Preferred stock, par value (in dollars per share) \| $ / shares				$ 0.001
Purchase price (in dollars per share) \| $ / shares				$ 8.76
Period following public announcement of beneficial ownership acquired by various persons resulting in rights becoming exercisable				10 days
Period following commencement of tender offer or exchange offer that would result in acquisition of beneficial ownership various persons resulting in rights becoming exercisable				10 days
Preferred stock dividend minimum if declared \| $ / shares				$ 1.00
Preferred stock rights ratio over common stock				1,000
Number of votes per share \| Vote				1,000
Ratio of consideration received in event of conversion or exchange transaction				1,000
Series B Junior Participating Preferred Stock \| Minimum
Stockholder Rights Plan
Beneficial ownership of common stock (as a percent)				4.99%