Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Tax Credit Carryforward [Line Items]
Tax Cuts and Jobs Act of 2017, tax benefit	$ 13,000
Excess tax benefit over compensation cost recognized, amount	600
Excess tax (benefits) or shortfall from share-based compensation		$ (80)	$ 626
Operating loss carryforward not expected to be realized under ASC subtopic 740-10	1,300
Tax credit carryforwards	5,613	4,234
Tax credit carryforwards valuation allowance	9,013	6,607
Permanent book to tax difference from goodwill impairment			8,700
Unrecognized tax benefits	5,271	$ 3,036	$ 2,963	$ 2,803
Unrecognized tax benefits that would impact effective tax rate	3,400
State
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	1,800
Tax credit carryforwards	12,800
Tax credit carryforwards valuation allowance	11,300
Federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 6,600