Warrants - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended					3 Months Ended			6 Months Ended		12 Months Ended
	Aug. 22, 2016 USD ($)	Jan. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Aug. 31, 2016 $ / shares shares	Aug. 31, 2015 $ / shares shares	Jul. 31, 2015 $ / shares shares	Jun. 30, 2018 USD ($) shares	Mar. 31, 2018 USD ($) Year $ / shares shares	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) shares	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2013 $ / shares shares
Common Stock Warrants [Line Items]
(Gain) loss related to change in fair value										$ (7,009)	$ 9,032
Fair value of warrants							$ 15,411			15,411		$ 22,420
Fair Value Measurement on Recurring Basis
Common Stock Warrants [Line Items]
Fair value of warrants							$ 15,411			$ 15,411		22,420
2016 Private Placement
Common Stock Warrants [Line Items]
Proceed from private placement and equity issuances, gross			$ 13,800
Fair value of warrants upon issuance	$ 2,700
Common Stock Warrants
Common Stock Warrants [Line Items]
Warrants issued | shares													128,231
Exercise price | $ / shares													$ 5.84
Common stock warrants, expiration date										Dec. 16, 2023
2015 Placement Common Stock Warrants | Insiders
Common Stock Warrants [Line Items]
Warrants issued | shares					198,760	198,760
Exercise price | $ / shares					$ 5.00	$ 5.00
Common stock warrants, expiry term					5 years	5 years
Class of warrant exercised | shares							5,498			5,498
Stock issued during period | shares							1,773			1,773
Placement warrants outstanding | shares							193,262			193,262
2018 Offering Warrants
Common Stock Warrants [Line Items]
Warrants issued | shares								1,418,116
Exercise price | $ / shares								$ 8.31
Common stock warrants, expiration date								Mar. 31, 2025
2018 Offering Warrants | 2018 Direct Registered Offering
Common Stock Warrants [Line Items]
Proceed from private placement and equity issuances, gross								$ 59,100
Fair value of warrants upon issuance								7,400
Proceeds from offering warrants								$ 6,600
2018 Offering Warrants | 2018 Direct Registered Offering | Expected Term
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs | Year								7
2018 Offering Warrants | 2018 Direct Registered Offering | Expected Volatility
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs								62.50%
2018 Offering Warrants | 2018 Direct Registered Offering | Risk-free Interest Rate
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs								2.80%
2018 Offering Warrants | 2018 Direct Registered Offering | Expected Dividend Yield
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs								0.00%
2016 Placement Warrants
Common Stock Warrants [Line Items]
Warrants issued | shares			1,380,745	1,380,745
Exercise price | $ / shares			$ 2.95	$ 2.95
Common stock warrants, expiry term			7 years	7 years
Placement warrants outstanding | shares							1,355,641			1,355,641
(Gain) loss related to change in fair value							$ 500		$ (2,800)	$ (3,100)	4,000
2016 Placement Warrants | Fair Value Measurement on Recurring Basis
Common Stock Warrants [Line Items]
Fair value of warrants							$ 6,829			$ 6,829		$ 9,933
2016 Placement Warrants | Expected Term
Common Stock Warrants [Line Items]
Expected term	7 years									5 years 2 months 12 days		5 years 8 months 12 days
2016 Placement Warrants | Expected Volatility
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs	61.60%									59.80%		62.10%
2016 Placement Warrants | Risk-free Interest Rate
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs	1.40%									2.70%		2.20%
2016 Placement Warrants | Expected Dividend Yield
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs	0.00%									0.00%		0.00%
2017 Placement Warrants
Common Stock Warrants [Line Items]
Warrants issued | shares		1,720,512
Exercise price | $ / shares		$ 3.17
Placement warrants outstanding | shares							1,711,123			1,711,123
Proceed from private placement and equity issuances, gross		$ 26,100
Fair value of warrants upon issuance		$ 3,400
(Gain) loss related to change in fair value							$ 700		$ (3,400)	$ (3,900)	$ 5,000
Warrant exercisable date		Jul. 31, 2017
Common stock warrants, expiry date		Jan. 31, 2024
2017 Placement Warrants | Fair Value Measurement on Recurring Basis
Common Stock Warrants [Line Items]
Fair value of warrants							$ 8,582			$ 8,582		$ 12,487
2017 Placement Warrants | Expected Term
Common Stock Warrants [Line Items]
Expected term		7 years								5 years 7 months 6 days		6 years 1 month 6 days
2017 Placement Warrants | Expected Volatility
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs		62.90%								60.00%		62.30%
2017 Placement Warrants | Risk-free Interest Rate
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs		2.20%								2.80%		2.30%
2017 Placement Warrants | Expected Dividend Yield
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs		0.00%								0.00%		0.00%