Revenue Recognition - Summary of Activity in Each of Product Revenue and Discount Categories (Detail) $ in Thousands	3 Months Ended
	Jun. 30, 2018 USD ($)
Revenue Recognition And Deferred Revenue [Abstract]
Balance at March 31, 2018	$ 1,405
Provision related to current period sales	442
Credits and adjustments made during the period	(396)
Balance at June 30, 2018	$ 1,451