LONG-TERM DEBT: (Details) (USD $)	6 Months Ended			1 Months Ended	6 Months Ended				0 Months Ended					6 Months Ended		6 Months Ended		12 Months Ended						6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013	Jul. 31, 2011 Interest rate swap July 25, 2011 derivative agreement	Sep. 30, 2013 Interest rate swap July 25, 2011 derivative agreement	Jul. 25, 2011 Interest rate swap July 25, 2011 derivative agreement	Sep. 30, 2013 Term loan credit agreement	Mar. 31, 2013 Term loan credit agreement	Oct. 09, 2013 Term loan credit agreement Subsequent event	Oct. 09, 2013 Term loan credit agreement Quarterly installments payable through September 2014 Subsequent event	Oct. 09, 2013 Term loan credit agreement Quarterly installments payable through September 2017 Subsequent event	Oct. 09, 2013 Term loan credit agreement Quarterly installments payable through June 2018 Subsequent event	Oct. 09, 2013 Term loan credit agreement Final payment due on October 9, 2018 Subsequent event	Sep. 30, 2013 Term loan credit agreement Quarterly installments payable through December 31, 2014	Sep. 30, 2013 Term loan credit agreement Final payment due on March 15, 2015	Sep. 30, 2013 Term loan credit agreement LIBOR	Sep. 30, 2013 Capital leases and installment payment obligations	Mar. 31, 2013 Capital leases and installment payment obligations	Sep. 30, 2013 Other debt and long-term liabilities	Mar. 31, 2013 Other debt and long-term liabilities	Sep. 30, 2013 Revolving credit facility	Mar. 31, 2013 Revolving credit facility	Oct. 09, 2013 Revolving credit facility Subsequent event	Sep. 30, 2013 Revolving credit facility LIBOR	Sep. 30, 2013 Revolving credit facility Alternative base rate	Sep. 30, 2013 Revolving credit facility Federal Funds rate
Long-term debt
Total long-term debt and capital leases	$ 244,273,000		$ 253,505,000				$ 215,000,000	$ 218,000,000									$ 16,130,000	$ 21,368,000	$ 13,143,000	$ 14,137,000
Less current installments	13,560,000		16,105,000
Long-term debt, excluding current installments	230,713,000		237,400,000
Long-term debt stated interest rate percentage, minimum																	3.00%	3.00%
Long-term debt stated interest rate percentage, maximum																	8.00%	8.00%
Maximum remaining maturity period of debt																	9 years	9 years
Aggregate amount of borrowing commitment							600,000,000		300,000,000												120,000,000		300,000,000
Amount borrowed									300,000,000
Existing debt repaid with proceeds of term loan	9,233,000	13,538,000							215,000,000
Required quarterly installment payments										3,800,000	7,500,000	11,300,000		1,500,000
Final payment of long-term debt													161,300,000		207,500,000
Long-term debt variable interest rate description																LIBOR								LIBOR	Alternative base rate	Federal Funds rate
Long-term debt basis spread on variable interest rate (as a percent)																3.00%								2.75%
Weighted-average interest rate on long-term debt (as a percent)							4.10%
Outstanding revolving credit borrowings																					0	0
Outstanding letters of credit																					2,200,000
Revolving credit facility dividend restrictions amount, maximum																					30,000,000
Fixed interest rate payable on swap (as a percent)						0.94%
Notional amount of derivative						150,000,000
Description of variable interest rate basis receivable on swap				LIBOR
LIBOR rate (as a percent)					0.25%
Fair market value of the derivative						0
Unrealized loss of the derivative recorded in other comprehensive income (loss)					$ (300,000)