FAIR VALUE OF FINANCIAL INSTRUMENTS: (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 31, 2017
Fair value of assets and liabilities
Other current assets	$ 47,394	$ 48,310
Fair value measurements on recurring basis | Total
Fair value of assets and liabilities
Other current assets	13,519
Total assets	13,519
Fair value measurements on recurring basis | Total | Level 1
Fair value of assets and liabilities
Other current assets	13,519
Total assets	13,519
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