9. STOCK- BASED COMPENSATION - Stock options activities (Details) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
STOCK- BASED COMPENSATION
Shares available for grant, Beginning	5,464,185	6,432,063	6,213,943
Options reserved (in shares)		1,085,818	1,156,419
Terminated plan (in shares)		(705,699)
Granted (in shares)	(1,029,684)	(1,362,798)	(969,913)
Forfeited (in shares)	9,800	14,801	31,614
Shares available for grant, Ending	4,444,301	5,464,185	6,432,063
Number of Shares Underlying Options Outstanding
Balance at the beginning of the period (in shares)	7,622,830	7,625,705	6,774,151
Granted (in shares)	1,029,684	1,362,798	969,913
Exercised (in shares)	(678,897)	(391,039)	(76,745)
Forfeited (in shares)	(99,350)	(974,634)	(41,614)
Balance at the end of the period (in shares)	7,874,267	7,622,830	7,625,705
Options vested and exercisable (in shares)	4,813,309
Options vested and expected to vest (in shares)	7,809,354
Weighted Average Remaining Contractual Life
Options weighted average remaining contractual life	5 years 7 months 2 days
Options vested and exercisable	3 years 10 months 13 days
Options vested and expected to vest	5 years 6 months 22 days
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 5.09	$ 5.08	$ 5.16
Granted (in dollars per share)	7.28	5.14	4.42
Exercised (in dollars per share)	4.22	3.96	4.19
Forfeited (in dollars per share)	5.06	5.53	4.82
Balance at the end of the period (in dollars per share)	5.45	$ 5.09	$ 5.08
Options vested and exercisable (in dollars per share)	5.25
Options vested and expected to vest (in dollars per share)	$ 5.44
Intrinsic Value
Exercised (in dollars)	$ 2,460,812	$ 855,160	$ 46,977
Options vested and exercisable (in dollars)	10,598,173
Options vested and expected to vest (in dollars)	$ 15,656,510