Income Taxes - Expiry Dates of Federal and State Income Tax Credit Carryforwards (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
U.S. federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 47,378
U.S. federal | U.S. Foreign Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 28,599
U.S. federal | U.S. Foreign Tax Credit | Minimum
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration year	2021
U.S. federal | U.S. Foreign Tax Credit | Maximum
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration year	2026
U.S. federal | U.S. research tax credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 18,758
U.S. federal | U.S. research tax credit | Minimum
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration year	2031
U.S. federal | U.S. research tax credit | Maximum
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration year	2036
U.S. federal | U.S. business tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 21
U.S. federal | U.S. business tax credits | Minimum
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration year	2031
U.S. federal | U.S. business tax credits | Maximum
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, expiration year	2036
California (U.S.)
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 20,088
California (U.S.) | State investment tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	1,148
California (U.S.) | State research tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 18,940