Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended	18 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Pre-tax losses	$ 23,195	$ 17,346	$ 45,240	$ 34,159
Benefit from income taxes	$ 235	$ 152	$ 320	$ 198
Percentage of annual research and development credit for cash			65.00%
Income tax rate					35.00%	21.00%

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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