Summary of Significant Accounting Policies - Inventory (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Inventory [Line Items]
Inventory write-down	$ 1,615	$ 2,713	$ 1,386
Inventory Valuation Reserve
Inventory [Line Items]
Benefits recorded for the usage of inventories previously reserved	$ (1,400)	$ (5,000)	$ (8,000)