Income taxes - Summary of Provision for (Benefit from) Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 0	$ 0	$ 0
State	7	324	115
Foreign	612	222	95
Deferred:
Federal	(966)	(307)	0
State	(198)	(52)	0
Foreign	0	0	0
Total income tax (benefit) expense	$ (545)	$ 187	$ 210

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

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