Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Income Taxes [Line Items]
Reversal of valuation			$ 101,500,000
Valuation allowance	$ 2,468,000	$ 2,418,000
Stock-based compensation tax deductions in excess of book compensation expense	12,038,000	3,567,000	606,000
Interest and penalties	$ 0	$ 0	$ 0
Earliest Tax Year
Income Taxes [Line Items]
Net operating loss carry forwards expiration period	2019
Latest Tax Year
Income Taxes [Line Items]
Net operating loss carry forwards expiration period	2035
Federal
Income Taxes [Line Items]
Net operating loss carry forwards	$ 167,300,000
Research and development credit carry forwards	13,700,000
Net operating loss carry forwards to stock-based compensation	167,300,000
Foreign
Income Taxes [Line Items]
Net operating loss carry forwards	46,900,000
State
Income Taxes [Line Items]
Research and development credit carry forwards	$ 7,800,000