Retirement Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Percentage of employees contribution matched by employer	50.00%
Percentage of employees gross pay eligible for employer match	6.00%
Employer matching contributions	$ 0.4	$ 0.5