Revenue Recognition - Summary of Activity in Each of Product Revenue and Discounts Categories (Detail) $ in Thousands	9 Months Ended
	Dec. 31, 2018 USD ($)
Revenue Recognition And Deferred Revenue [Abstract]
Balance at March 31, 2018	$ 1,405
Provision related to current period revenue	1,526
Credits and adjustments made during the period	(1,446)
Balance at December 31, 2018	$ 1,485