Debt - Schedule of Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Mar. 31, 2018
Debt Disclosure [Abstract]
Total debt	$ 120,000	$ 84,000
Long-term debt	120,000	84,000
Deferred debt costs and royalty liability, net of amortization	44	1,063
Long-term debt, less current portion	$ 120,044	$ 85,063