Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Income Tax Contingency [Line Items]
Unrecognized tax benefits			$ 399	$ 377	$ 432
Federal corporate income tax rate	21.00%	35.00%	21.00%	21.00%	28.06%
Net operating loss carryforward, subject to expiration			$ 104,800
Net operating loss carryforward, not subject to expiration			16,800
Net operating losses utilized			1,700
Research and development tax credit carryforwards			7,800
Valuation allowance against certain deferred tax assets			34,830	$ 32,538
Increase in valuation allowance			2,300
Gross unrecognized tax benefits	$ 8,701		11,310	$ 9,913	$ 8,701	$ 8,656
Unrecognized tax benefits that, if recognized, would favorably affect effective income tax rate in future periods			1,900
Reduction to tax credit carryforwards			3,300
Unrecognized tax benefits decrease as a result of the expiration of certain statutes			300
United States
Income Tax Contingency [Line Items]
Net operating loss carryforwards			121,600
Europe and Israel
Income Tax Contingency [Line Items]
Net operating loss carryforwards			$ 30,900