Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model (Detail)	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Risk-free interest rate, Minimum	0.43%	1.89%
Risk-free interest rate, Maximum	0.60%	2.42%
Expected volatility, Minimum	73.10%	72.68%
Expected volatility, Maximum	73.90%	78.85%
Expected dividend yield	0.00%	0.00%
Maximum [Member]
Expected life in years	6 years 3 months	6 years 3 months
Minimum [Member]
Expected life in years	6 years	5 years 9 months