Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Tax Credit Carryforward [Line Items]
Tax Cuts and Jobs Act of 2017, tax benefit		$ 13,000
Excess tax benefit over compensation cost recognized, amount	$ 200	600
Excess tax (benefits) or shortfall from share-based compensation			$ (80)
Operating loss carryforward not expected to be realized under ASC subtopic 740-10	1,900
Tax credit carryforwards	288	5,613
Tax credit carryforwards valuation allowance	9,083	9,013
Unrecognized tax benefits	5,283	$ 5,271	$ 3,036	$ 2,963
Unrecognized tax benefits that would impact effective tax rate	3,600
State
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	2,000
Tax credit carryforwards	13,000
Tax credit carryforwards valuation allowance	11,500
Federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 2,600