Nature of the Business and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Segment Region	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment	1
Number of geographic regions | Region	1
Original maturities	Three months or less
Restricted cash	$ 0.8	$ 0.7
Advertising expenses	$ 4.5	1.0
Performance period	5 years
Tax incentive awarded	$ 3.8
State research and development tax credits monetized	3.4
Amount of tax incentives required to repay	1.3
Amount of benefit recognized	$ 0.1	$ 0.7	$ 0.4
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected remaining maturities period of marketable securities classified as available-for-sale	3 months