Shareholders' Equity - Schedule of Stock-based Compensation Expense for Equity Classified Instruments (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restricted Share Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation charge	$ 411,000	$ 0	$ 503,000	$ 0
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation for equity classified instruments	3,346,000	1,507,000	5,496,000	2,633,000
Change in fair value of liability classified equity instruments	(107,000)	1,548,000	(1,900,000)	1,968,000
Stock based compensation for equity classed instruments and change in fair value of liability classed equity instruments	3,239,000	3,055,000	3,596,000	4,601,000
General and Administrative Expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation for equity classified instruments	4,046,000	1,579,000	6,497,000	3,070,000
Change in fair value of liability classified equity instruments	(310,000)	4,800,000	(5,799,000)	6,127,000
Stock based compensation for equity classed instruments and change in fair value of liability classed equity instruments	3,736,000	6,379,000	698,000	9,197,000
Finance Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Change in fair value of liability classified equity instruments	(2,000)	0	(36,000)	68,000
Stock based compensation for equity classed instruments and change in fair value of liability classed equity instruments	$ (2,000)	$ 0	$ (36,000)	$ 68,000