OTHER ACCRUED EXPENSES: (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
Other Accrued Expenses [Abstract].
Liabilities of non-qualified retirement plan	$ 15,223	$ 13,551
Other accrued expenses	29,211	26,073
Other accrued expenses	$ 44,434	$ 39,624