FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Available-for-sale Investments [Abstract]
Asset transfers Level 1 to Level 2	$ 0	$ 0	$ 0	$ 0
Asset transfers Level 2 to Level 1	0	0	0	0
Asset transfers into Level 3	0	0	0	0
Asset transfers out of Level 3	0	0	0	0
Liabilities [Abstract]
Liabilities transfers Level 1 to Level 2	0	0	0	0
Liabilities transfers Level 2 to Level 1	0	0	0	0
Liability transfers into Level 3	0	0	0	0
Liability transfers out of Level 3	0	$ 0	0	$ 0
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents	7,098		7,098		$ 584
Available-for-sale Investments [Abstract]
Commercial paper	9,954		9,954
Corporate bonds	45,226		45,226		6,377
Municipal bonds	656		656		662
Total assets at fair value	62,934		62,934		7,623
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member]
Assets [Abstract]
Cash equivalents	7,098		7,098		584
Available-for-sale Investments [Abstract]
Commercial paper	0		0
Corporate bonds	0		0		0
Municipal bonds	0		0		0
Total assets at fair value	7,098		7,098		584
Liabilities [Abstract]
Total liabilities at fair value	0		0		0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs Level 2 [Member]
Assets [Abstract]
Cash equivalents	0		0		0
Available-for-sale Investments [Abstract]
Commercial paper	9,954		9,954
Corporate bonds	45,226		45,226		6,377
Municipal bonds	656		656		662
Total assets at fair value	55,836		55,836		7,039
Liabilities [Abstract]
Total liabilities at fair value	0		0		0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs Level 3 [Member]
Assets [Abstract]
Cash equivalents	0		0		0
Available-for-sale Investments [Abstract]
Commercial paper	0		0
Corporate bonds	0		0		0
Municipal bonds	0		0		0
Total assets at fair value	0		0		0
Liabilities [Abstract]
Total liabilities at fair value	$ 0		$ 0		$ 0