Stockholders' Equity (Deficit) - Additional Information (Detail) $ / shares in Units, $ in Thousands						1 Months Ended			3 Months Ended		12 Months Ended
	Oct. 29, 2018 USD ($) shares	Sep. 20, 2018 USD ($) shares	Feb. 27, 2018 USD ($) shares	Jan. 22, 2018 USD ($) shares	Dec. 20, 2016 USD ($) $ / shares shares	Nov. 30, 2018 USD ($) $ / shares	Sep. 30, 2018 USD ($) shares	Jan. 31, 2017 $ / shares shares	Nov. 30, 2018 $ / shares shares	Mar. 31, 2018 $ / shares shares	Dec. 31, 2018 USD ($) PrivatePlacement	Dec. 31, 2017 shares	May 22, 2017 shares	Jan. 31, 2017 $ / shares	Dec. 31, 2016 shares
Class of Stock [Line Items]
Common stock, shares authorized							50,000,000					50,000,000	50,000,000		13,000,000
Capital stock, shares authorized							50,500,000
Preferred stock, shares authorized							500,000					500,000
Common stock issued, price per share | (per share)								$ 0.83						$ 0.022
Private placement amount received | $					$ 1,000
Common stock
Class of Stock [Line Items]
Stock issued, shares					1,397,300			249,632
CHESS Depositary Interests
Class of Stock [Line Items]
Stock issued, shares					69,865,000			12,481,600
Common stock issued, price per share | $ / shares					$ 0.22
Tranche One
Class of Stock [Line Items]
Private placement amount received | $							$ 2,200
Tranche Two | Scenario, Forecast
Class of Stock [Line Items]
Private placement amount received | $						$ 2,800
First Quarter 2018 Placement | Common stock
Class of Stock [Line Items]
Stock issued, shares										8,120,057
First Quarter 2018 Placement | CHESS Depositary Interests
Class of Stock [Line Items]
Stock issued, shares										406,002,869
Common stock issued, price per share | $ / shares										$ 0.035
First Quarter 2018 Placement | Tranche One
Class of Stock [Line Items]
Private placement amount received | $				$ 781
Stock issuance costs | $				$ 63
First Quarter 2018 Placement | Tranche One | Common stock
Class of Stock [Line Items]
Stock issued, shares				569,341
First Quarter 2018 Placement | Tranche One | CHESS Depositary Interests
Class of Stock [Line Items]
Stock issued, shares				28,467,063
First Quarter 2018 Placement | Tranche Two
Class of Stock [Line Items]
Private placement amount received | $			$ 824
Stock issuance costs | $			$ 39
First Quarter 2018 Placement | Tranche Two | Common stock
Class of Stock [Line Items]
Stock issued, shares			606,271
First Quarter 2018 Placement | Tranche Two | CHESS Depositary Interests
Class of Stock [Line Items]
Stock issued, shares			30,313,556
First Quarter 2018 Placement | Tranche Two | CHESS Depositary Interests | Board Member
Class of Stock [Line Items]
Stock issued, shares			2,921,800
First Quarter 2018 Placement | Tranche Two | CHESS Depositary Interests | Crystal Amber Fund
Class of Stock [Line Items]
Stock issued, shares			27,391,756
Private Placement | Scenario, Forecast
Class of Stock [Line Items]
Private placement amount received | $											$ 6,610
Number of private placements | PrivatePlacement											2
Autumn 2018 Placement | Common stock | Scenario, Forecast
Class of Stock [Line Items]
Stock issued, shares									6,944,445
Autumn 2018 Placement | CHESS Depositary Interests | Scenario, Forecast
Class of Stock [Line Items]
Stock issued, shares									347,222,250
Autumn 2018 Placement | CHESS Depositary Interests | Existing Investors | Scenario, Forecast
Class of Stock [Line Items]
Common stock issued, price per share | $ / shares						$ 0.020			$ 0.020
Autumn 2018 Placement | Tranche One
Class of Stock [Line Items]
Private placement amount received | $		$ 2,200
Stock issuance costs | $		$ 56
Autumn 2018 Placement | Tranche One | Common stock
Class of Stock [Line Items]
Stock issued, shares		3,000,000
Autumn 2018 Placement | Tranche One | CHESS Depositary Interests
Class of Stock [Line Items]
Stock issued, shares		150,000,000
Autumn 2018 Placement | Tranche Two
Class of Stock [Line Items]
Private placement amount received | $	$ 2,800
Autumn 2018 Placement | Tranche Two | Common stock
Class of Stock [Line Items]
Stock issued, shares	3,944,445
Autumn 2018 Placement | Tranche Two | CHESS Depositary Interests
Class of Stock [Line Items]
Stock issued, shares	197,222,250
Autumn 2018 Placement | Tranche Two | CHESS Depositary Interests | Existing Investors | United States | Subsequent Event
Class of Stock [Line Items]
Stock issued, shares	23,819,450
Autumn 2018 Placement | Tranche Two | CHESS Depositary Interests | Existing Investors | Australia | Subsequent Event
Class of Stock [Line Items]
Stock issued, shares	5,208,350
Autumn 2018 Placement | Tranche Two | CHESS Depositary Interests | Crystal Amber Fund | Subsequent Event
Class of Stock [Line Items]
Stock issued, shares	168,194,450