FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Assets [Abstract]
Asset transfers Level 1 to Level 2	$ 0	$ 0	$ 0
Asset transfers Level 2 to Level 1	0	0	0
Asset transfers into Level 3	0	0	0
Asset transfers out of Level 3	0	0	0
Liabilities [Abstract]
Liabilities transfers Level 1 to Level 2	0	0	0
Liabilities transfers Level 2 to Level 1	0	0	0
Liability transfers into Level 3	0	0	0
Liability transfers out of Level 3	0	0	$ 0
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Cash equivalents	590	584
Available-for-sale Investments [Abstract]
Commercial paper	9,251
Corporate bonds	66,648	6,377
Municipal bonds	650	662
Total assets at fair value	77,139	7,623
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets Level 1 [Member]
Assets [Abstract]
Cash equivalents	590	584
Available-for-sale Investments [Abstract]
Commercial paper	0
Corporate bonds	0	0
Municipal bonds	0	0
Total assets at fair value	590	584
Liabilities [Abstract]
Total liabilities at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs Level 2 [Member]
Assets [Abstract]
Cash equivalents	0	0
Available-for-sale Investments [Abstract]
Commercial paper	9,251
Corporate bonds	66,648	6,377
Municipal bonds	650	662
Total assets at fair value	76,549	7,039
Liabilities [Abstract]
Total liabilities at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs Level 3 [Member]
Assets [Abstract]
Cash equivalents	0	0
Available-for-sale Investments [Abstract]
Commercial paper	0
Corporate bonds	0	0
Municipal bonds	0	0
Total assets at fair value	0	0
Liabilities [Abstract]
Total liabilities at fair value	$ 0	$ 0