Income Taxes - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Tax Credit Carryforward [Line Items]
Deferred tax assets, net	$ 15.8
Unrecognized tax benefits recognized during period	3.8
Unrecognized tax benefits	3.9
Increase in unrecognized tax benefits in next twelve months	0.2
Research and development tax credit studies	$ 2.1
Overall effective tax rate, after discrete period adjustments	(7.90%)
Effective tax rate, before discrete period adjustment	22.80%
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
Restricted Stock Units (RSUs)
Tax Credit Carryforward [Line Items]
Discrete tax benefit, stock-based compensation	6.1
Stock Options
Tax Credit Carryforward [Line Items]
Discrete tax benefit, stock-based compensation	$ 3.4