Background and Organization - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Net loss	$ (30,798)	$ (21,990)	$ (64,159)	$ (26,804)
Net cash used from operating activities			(49,552)	$ (48,838)
Cash and cash equivalents	$ 122,053		$ 122,053		$ 167,432

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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