Income Taxes - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Tax Credit Carryforward [Line Items]
Deferred tax assets, net	$ 20.1
Research and development tax credit studies	15.6
Unrecognized tax benefits	$ 4.4
Overall effective tax rate, after discrete period adjustments	17.60%
Effective tax rate, before discrete period adjustment	42.90%
Discrete tax benefit, stock-based compensation	$ 1.0
Federal
Tax Credit Carryforward [Line Items]
Unrecognized tax benefits	4.3
State
Tax Credit Carryforward [Line Items]
Unrecognized tax benefits	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, valuation allowance	$ 1.6