11. STOCK-BASED COMPENSATION - Weighted average assumptions (Details) - USD ($)	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Stock-based compensation
Expected life	5 years	5 years	5 years
Dividend yield (as a percent)	0.00%
Other information
Income tax benefit recognized from allocation of share-based compensation expense	$ 0	$ 0
Windfall tax benefits realized	0	$ 0
Unrecognized compensation costs	$ 5,200,000
Weighted average period of recognition of unrecognized compensation costs	1 year 11 months 23 days
Weighted average fair value per underlying share of options granted (in dollars per share)	$ 2.29	$ 2.55	$ 2.86
Employee stock options
Stock-based compensation
Risk-free interest rate, low end of range (as a percent)	0.66%	0.22%	1.35%
Risk-free interest rate, high end of range (as a percent)	1.62%	0.42%	2.30%
Expected life	5 years	5 years	5 years
Volatility, low end of range (as a percent)	47.70%	41.90%	36.50%
Volatility, high end of range (as a percent)	49.10%	47.60%	39.70%
Employee stock purchase plan options
Stock-based compensation
Risk-free interest rate, low end of range (as a percent)	0.04%	0.12%	1.58%
Risk-free interest rate, high end of range (as a percent)	0.07%	0.15%	2.43%
Expected life	6 months	6 months	6 months
Volatility, low end of range (as a percent)	45.60%	67.10%	33.50%
Volatility, high end of range (as a percent)	57.40%	68.60%	43.10%