LONG-TERM DEBT (Details) (USD $) In Thousands, unless otherwise specified					1 Months Ended	12 Months Ended							12 Months Ended				12 Months Ended		12 Months Ended						12 Months Ended			12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Bank credit facilities	Mar. 31, 2012 Bank credit facilities	Jun. 30, 2012 Credit Agreement	Mar. 31, 2013 Credit Agreement	Mar. 31, 2013 Credit Agreement Minimum	Mar. 31, 2013 Credit Agreement Maximum	Mar. 31, 2013 Credit Agreement LIBOR	Mar. 31, 2013 Credit Agreement LIBOR Minimum	Mar. 31, 2013 Credit Agreement LIBOR Maximum	Mar. 31, 2013 Credit Agreement Alternate base rate	Mar. 31, 2013 Credit Agreement One-month LIBOR rate	Mar. 31, 2013 Credit Agreement Federal Funds effective rate	Mar. 31, 2013 Credit Agreement Federal Funds effective rate Minimum	Mar. 31, 2013 Credit Agreement Federal Funds effective rate Maximum	Mar. 31, 2013 Credit Agreement Prime lending rate	Mar. 31, 2013 A&B Credit Facility	Mar. 31, 2013 Auxiliary Bank Facilities item	Mar. 31, 2013 Auxiliary Bank Facility one	Mar. 31, 2013 Auxiliary Bank Facility two	Mar. 31, 2013 Term equipment notes	Mar. 31, 2012 Term equipment notes	Mar. 31, 2013 Term equipment notes Minimum	Mar. 31, 2013 Term equipment notes Maximum	Mar. 31, 2013 Other	Mar. 31, 2012 Other	Mar. 31, 2013 Other Maximum
LONG-TERM DEBT
Long-term debt	$ 123,684	$ 163,746	$ 73,793	$ 93,793																		$ 47,875	$ 65,310			$ 2,016	$ 4,643
Current portion of long-term debt	(20,550)	(23,596)
Long-term debt, net of current portion	103,134	140,150
Maximum borrowing capacity, before amendment					285,000
Increase in maximum borrowing capacity					100,000
Maximum borrowing capacity					385,000													25,000		5,000	5,000
Outstanding borrowings						70,000												1,473	2,320
Weighted average interest rate (as a percent)						1.70%												2.80%	2.00%
Leverage Ratio								2.75
Variable interest rate basis									LIBOR				LIBOR rate for a one-month interest period	Federal Funds effective rate			administrative agent bank's prime lending rate
Interest rate margin (as a percent)									1.50%	1.25%	2.25%	0.00%	1.50%	0.50%
Additional interest margin (as a percent)															0.00%	0.75%
Annual commitment fee (as a percent)						0.25%	0.25%	0.375%
Number of revolving credit facilities																			2
Interest rate (as a percent)																								2.80%	4.10%
Period of principal payments plus interest from the date of issuance																									7 years			16 years
Available credit under existing credit facilities	242,648
Debt obligations
2014	20,550
2015	13,775
2016	10,974
2017	2,801
2018	74,862
Thereafter	$ 722