8. STOCK- BASED COMPENSATION - Stock options activities (Details)	6 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
STOCK- BASED COMPENSATION
Shares available for grant, Beginning	5,464,185
Granted (in shares)	(658,983)
Forfeited (in shares)	9,800
Shares available for grant, Ending	4,815,002
Number of Shares Underlying Options Outstanding
Balance at the beginning of the period (in shares)	7,622,830
Granted (in shares)	658,983
Exercised (in shares)	(394,490)
Forfeited (in shares)	(92,700)
Balance at the end of the period (in shares)	7,794,623
Options vested and exercisable (in shares)	4,851,100
Options vested and expected to vest (in shares)	7,719,879
Weighted Average Remaining Contractual Life
Options weighted average remaining contractual life	5 years 8 months 27 days
Options vested and exercisable	4 years 7 days
Options vested and expected to vest	5 years 8 months 12 days
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share) | $ / shares	$ 5.09
Granted (in dollars per share) | $ / shares	7.28
Exercised (in dollars per share) | $ / shares	4.48
Forfeited (in dollars per share) | $ / shares	5.02
Balance at the end of the period (in dollars per share) | $ / shares	5.30
Options vested and exercisable (in dollars per share) | $ / shares	5.18
Options vested and expected to vest (in dollars per share) | $ / shares	$ 5.30
Intrinsic Value
Exercised (in dollars) | $	$ 1,291,881
Options vested and exercisable (in dollars) | $	10,344,300
Options vested and expected to vest (in dollars) | $	$ 15,453,096