Tax Loss and Credit Carryforwards (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
U.S. federal
Tax Credit Carryforward [Line Items]
Tax loss carryforwards		$ 34,268	$ 29,853
Tax loss carryforwards, Expiration year		Dec. 31, 2027
State and Local
Tax Credit Carryforward [Line Items]
Tax loss carryforwards		$ 21,258	18,147
Tax loss carryforwards, Expiration year		Dec. 31, 2027
Israeli
Tax Credit Carryforward [Line Items]
Tax loss carryforwards		$ 15,204	15,382
Tax loss carryforwards, Expiration year		Indefinite
Illinois Edge
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	[1]	$ 15,523	11,992
Tax credit carryforwards, Expiration year	[1]	Dec. 31, 2018
Research and development | U.S. federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards		$ 5,359	1,986
Tax credit carryforwards, Expiration year		Dec. 31, 2028
Research and development | State and Local
Tax Credit Carryforward [Line Items]
Tax credit carryforwards		$ 1,401	$ 1,710
Tax credit carryforwards, Expiration year		Dec. 31, 2018

[1] Amounts are before the federal benefit of state tax