Income Taxes - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Tax Credit Carryforward [Line Items]
Deferred tax assets, net	$ 14.2
Unrecognized tax benefits recognized during period	3.6
Unrecognized tax benefits	3.7
Increase in unrecognized tax benefits in next twelve months	0.2
Research and development tax credit studies	$ 2.0
Overall effective tax rate, after discrete period adjustments	12.90%
Effective tax rate, before discrete period adjustment	23.10%
Discrete tax benefit, stock-based compensation	$ 1.6
State
Tax Credit Carryforward [Line Items]
Unrecognized tax benefits recognized during period	0.1
Expiring in 2019
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	1.2
Research and Development Credits
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	$ 17.0