LONG-TERM DEBT: (Details) - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2016	Mar. 31, 2016	Mar. 10, 2014
Long-term debt
Total long-term debt and capital leases	$ 238,682	$ 192,856
Less current installments	36,050	32,243
Less deferred debt financing costs	1,834	2,716
Long-term debt, excluding current installments and deferred debt financing costs	200,798	157,897
Long-term debt	$ 200,798	157,897
LIBOR rate (as a percent)	0.98%
March 10, 2014 derivative agreement | Cash flow hedge
Long-term debt
Fixed interest rate payable on swap (as a percent)			0.98%
Notional amount of derivative			$ 50,000
Fair market value of the derivative	$ 0
LIBOR | March 10, 2014 derivative agreement
Long-term debt
Long-term debt variable interest rate description	LIBOR
Term loans
Long-term debt
Total long-term debt and capital leases	$ 162,500	185,000
Aggregate amount of borrowing commitment	$ 300,000
Weighted-average interest rate on long-term debt (as a percent)	2.60%
Term loans | Quarterly installments payable through September 2017
Long-term debt
Required quarterly installment payments	$ 7,500
Term loans | Quarterly installments payable through June 2018
Long-term debt
Required quarterly installment payments	11,300
Term loans | Final payment due on October 9, 2018
Long-term debt
Final payment of long-term debt	$ 106,300
Term loans | LIBOR
Long-term debt
Long-term debt basis spread on variable interest rate (as a percent)	1.75%
Long-term debt variable interest rate description	LIBOR
Term loans | Alternative base rate
Long-term debt
Long-term debt variable interest rate description	Alternative base rate
Revolving credit facility
Long-term debt
Total long-term debt and capital leases	$ 70,000
Aggregate amount of borrowing commitment	$ 300,000
Weighted-average interest rate on long-term debt (as a percent)	2.40%
Revolving credit facility dividend restrictions amount, maximum	$ 30,000
Revolving credit facility | LIBOR
Long-term debt
Long-term debt basis spread on variable interest rate (as a percent)	1.75%
Long-term debt variable interest rate description	LIBOR
Revolving credit facility | Alternative base rate
Long-term debt
Long-term debt variable interest rate description	Alternative base rate
Other debt and long-term liabilities
Long-term debt
Total long-term debt and capital leases	$ 6,182	$ 7,856