Goodwill and Purchased Intangibles Assets - Schedule of Purchased Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Net Carrying Amount	$ 1,508	$ 2,499
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,900	4,900
Accumulated Amortization	(3,392)	(2,401)
Net Carrying Amount	$ 1,508	$ 2,499