Income Taxes - Expiry Dates of Federal and State Income Tax Credit Carryforwards (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
U.S. federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 23,812
U.S. federal | U.S. foreign tax credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 15,793
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	$ 7,819
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
U.S. federal | U.S. AMT tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 179
California (U.S.)
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	13,897
California (U.S.) | State investment tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	820
California (U.S.) | State research tax credits
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 13,077