7. STOCK- BASED COMPENSATION - Weighted average assumptions (Details) - $ / shares	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation
Weighted average fair value per underlying share of options granted (in dollars per share)	$ 1.48	$ 1.79	$ 1.70	$ 2.10
Employee Consultants And Directors Stock Options
Stock-based compensation
Risk-free interest rate (as a percent)	1.56%	1.60%
Risk-free interest rate, low end of range (as a percent)			1.52%	1.60%
Risk-free interest rate, high end of range (as a percent)			1.57%	1.70%
Expected life	5 years	5 years	5 years	5 years
Volatility (as a percent)	36.30%	41.30%
Volatility, low end of range (as a percent)			36.30%	41.30%
Volatility, high end of range (as a percent)			38.00%	44.80%
Dividend yield (as a percent)	0.00%	0.00%	0.00%	0.00%
Employee stock purchase plan
Stock-based compensation
Risk-free interest rate (as a percent)	0.15%	0.05%		0.05%
Risk-free interest rate, low end of range (as a percent)			0.09%
Risk-free interest rate, high end of range (as a percent)			0.15%
Expected life	6 months	6 months		6 months
Volatility (as a percent)	27.90%	38.00%
Volatility, low end of range (as a percent)			26.30%	30.80%
Volatility, high end of range (as a percent)			27.90%	38.00%
Dividend yield (as a percent)	0.00%	0.00%	0.00%	0.00%