OTHER ACCRUED EXPENSES: (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019
Other Accrued Expenses [Abstract].
Liabilities of non-qualified retirement plan	$ 14,746	$ 14,970
Short-term lease liabilities	8,443	0
PDP performance plan liability (see Note 7)	6,799	0
DPM consideration holdback (see Note 7)	2,060	0
Other miscellaneous accrued expenses	23,676	25,946
Other accrued expenses	$ 55,724	$ 40,916