FAIR VALUE OF FINANCIAL INSTRUMENTS: (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Mar. 31, 2018
Fair value of assets and liabilities
Other current assets	$ 27,366	$ 20,173
Fair value measurements on recurring basis | Total
Fair value of assets and liabilities
Other current assets	13,706
Total assets	13,706
Fair value measurements on recurring basis | Total | Level 1
Fair value of assets and liabilities
Other current assets	13,706
Total assets	13,706
Fair value measurements on recurring basis | Total | Level 2
Fair value of assets and liabilities
Other current assets	0
Total assets	0
Fair value measurements on recurring basis | Total | Level 3
Fair value of assets and liabilities
Other current assets	0
Total assets	$ 0