OTHER ACCRUED EXPENSES: (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018
Other Accrued Expenses [Abstract].
Liabilities of non-qualified retirement plan	$ 15,263		$ 14,970
Short-term leases liabilities	8,443		0
PDP performance plan liability	19,500		0
Other miscellaneous accrued expenses	27,723		25,946
Other accrued expenses	$ 70,929	$ 40,916	$ 40,916