Exercise price per share or per unit of warrants or rights outstanding.

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Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

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Amount of expense (income) related to adjustment to fair value of warrant liability.

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The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

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The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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Expiration date of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in CCYY-MM-DD format.

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Non Operating Income Expense Inducement Of Warrants.

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Placement agent fees and other related expenses.

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Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	Sep. 12, 2019	Nov. 11, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of securities into which the class of warrant converted		18,939,394
Warrant Exercise Per share		$ 2.64
Fair Value Assumptions Expected volatility Rate Maximum				85.00%	84.71%	81.03%
Fair Value Assumptions Risk Free Interest Rate Maximum				2.53%	3.06%	2.27%
Fair Value Assumptions Expected Term1				5 years	6 years	6 years
Net Proceeds from Underwriting				$ 6,085	$ 47,101	$ 47,270
Proceeds from private placement	$ 52,500
Non-cash inducement warrant expense			$ (60,751)	$ 60,751
MD Anderson Warrant [Member]
Number of securities into which the class of warrant converted				3,333,333
Warrant Exercise Per share				$ 0.001
Grant Date Fair Value of a warrant				$ 14,500
Warrant Expiry date				Dec. 31, 2026
Securities Purchase Agreement [Member]
Net Proceeds from Underwriting		$ 47,100		$ 47,100
Private Placement [Member]
Number of securities into which the class of warrant converted	17,803,031			18,939,394
Warrant Exercise Per share	$ 3.01			$ 3.01
Grant Date Fair Value of a warrant				$ 18,400
Fair Value Assumptions Expected volatility Rate Maximum				71.00%
Fair Value Assumptions Risk Free Interest Rate Maximum				2.99%
Placement agent fees and other expenses	$ 1,100
Private Placement [Member] \| New Warrants [Member]
Number of securities into which the class of warrant converted	17,803,031
Warrant Exercise Per share	$ 7.00
Non-cash inducement warrant expense	$ 60,800			$ 60,800