Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended	15 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Pre-tax losses	$ 22,045	$ 16,813
Benefit from income taxes	$ 85	$ 46
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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