Employee Benefits Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Maximum percentage of employee gross pay for defined contribution plan under Section 401(k)	50.00%
Employer match of employee's deferral	100.00%
Employer matching contribution for defined contribution plan under Section 401(k)	5.00%
Total company matching contributions	$ 2.4	$ 2.3	$ 2.5