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Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Jul. 29, 2019	Dec. 31, 2018
Cash and cash equivalents		$ 43,563		$ 61,729
Accumulated deficit		(594,383)		$ (566,329)
Research and development expense related to joint venture		$ 35,000
Private Placement [Member]
Number of securities into which the class of warrant converted		18,939,394
Warrant Exercise Per share		$ 3.01
Subsequent Event [Member]
Proceeds from private placement	$ 45,000
Subsequent Event [Member] \| Private Placement [Member]
Number of securities into which the class of warrant converted			15,015,152
Warrant Exercise Per share			$ 3.01
Subsequent Event [Member] \| New Warrants [Member] \| Private Placement [Member]
Number of securities into which the class of warrant converted			15,015,152
Warrant Exercise Per share			$ 7.00