LONG-TERM DEBT: (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Total long-term debt and capital leases	$ 230,000	$ 233,293
Less current installments	0	1,583
Less deferred debt financing costs	3,693	3,873
Long-term debt, excluding current installments and deferred debt financing costs	226,307	227,837
Revolving credit facility
Debt Instrument [Line Items]
Total long-term debt and capital leases	230,000	230,000
Other debt and long-term liabilities
Debt Instrument [Line Items]
Total long-term debt and capital leases	$ 0	$ 3,293