Nature of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands						1 Months Ended											2 Months Ended	3 Months Ended			6 Months Ended	12 Months Ended
	May 15, 2019 USD ($)	Apr. 30, 2019	Nov. 30, 2018	Dec. 20, 2016 USD ($) $ / shares shares	Aug. 21, 2015	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	May 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jan. 31, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jan. 31, 2017 USD ($) $ / shares shares	May 31, 2014 USD ($)	Sep. 30, 2011 USD ($)	Aug. 31, 2013 USD ($)	Mar. 31, 2019 USD ($) Segment	Mar. 31, 2018 USD ($) shares	Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2018 USD ($)	Jan. 31, 2017 $ / shares
Nature Of Operations [Line Items]
Number of reportable segments | Segment																		1
Percentage of reducing headcount					46.00%
Non-recurring charges																					$ 1,100
Issuance of shares, value											$ 1,600	$ 1,600			$ 30,800	$ 72,500	$ 52,500		$ 1,503
Repayment of convertible term promissory notes																$ 6,000
Common stock issued, price per share | (per share)														$ 0.83									$ 0.022
Private placement amount received				$ 1,000
Proceeds from issuance of common stock														$ 200					1,503
Accumulated deficit						$ (269,490)	$ (267,159)											$ (269,490)				$ (267,159)
Working capital deficit						(5,500)												(5,500)
Cash used in operating activities																		(3,464)	(1,974)
Cash and cash equivalents						$ 1,286	$ 3,806											1,286				3,806
2019 Warrant
Nature Of Operations [Line Items]
Maturity description						will expire on the fifth anniversary of the date of issuance.
Tranche One
Nature Of Operations [Line Items]
Private placement amount received									$ 2,200
Tranche Two
Nature Of Operations [Line Items]
Private placement amount received								$ 2,800
Private Placement
Nature Of Operations [Line Items]
Issuance of shares, value									$ 5,000
Private placement amount received																						6,610
2017 Senior Secured Convertible Promissory Note
Nature Of Operations [Line Items]
Debt principal amount													$ 5,000
Interest rate during period													5.00%
Maturity Date			Dec. 31, 2018			May 01, 2019	Mar. 31, 2019						Dec. 31, 2018
Accrued interest							$ 394															$ 394
2017 Senior Secured Convertible Promissory Note | Subsequent Event
Nature Of Operations [Line Items]
Maturity Date		Apr. 30, 2019
2018 Senior Secured Convertible Promissory Note and Warrant
Nature Of Operations [Line Items]
Debt principal amount										$ 1,750
Maturity Date										May 30, 2023
2018 Senior Secured Convertible Promissory Note
Nature Of Operations [Line Items]
Interest rate during period										10.00%
2019 Senior Secured Convertible Promissory Note and Warrant
Nature Of Operations [Line Items]
Debt principal amount						$ 1,000												$ 1,000
2019 Senior Secured Convertible Promissory Note and Warrant | Subsequent Event
Nature Of Operations [Line Items]
Debt principal amount	$ 3,000
Maturity description	will expire on the fifth anniversary of the Full Funding Date.
Debt payment terms	The $3.0 million payment will be made in several tranches.
2019 Senior Secured Convertible Promissory Note
Nature Of Operations [Line Items]
Interest rate during period						10.00%
Maturity Date						Mar. 15, 2024
2019 Senior Secured Convertible Promissory Note | Subsequent Event
Nature Of Operations [Line Items]
Interest rate during period	10.00%
Common stock
Nature Of Operations [Line Items]
Issuance of shares, value																			$ 12
Stock issued, shares | shares				1,397,300										249,632					1,175,612
CHESS Depositary Interests
Nature Of Operations [Line Items]
Stock issued, shares | shares				69,865,000										12,481,600
Common stock issued, price per share | $ / shares				$ 0.022
Restructuring Charges
Nature Of Operations [Line Items]
Non-recurring charges																				$ 400
Employee Severance
Nature Of Operations [Line Items]
Non-recurring charges																					600
Facility Closing
Nature Of Operations [Line Items]
Non-recurring charges																					$ 100