Sale of Receivables (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012 Programs	Mar. 31, 2011	Mar. 31, 2012 Asset-backed Securities Program Number One [Member]	Feb. 29, 2012 Asset-backed Securities Program Number One [Member]	Mar. 31, 2012 Asset Backed Securities Program Number Two [Member]
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets [Line Items]
Number of accounts receivable securitiztion programs	2
Receivables sold, face value discounted, percentage	100.00%
Trade receivables sold, maximum amount			$ 250,000	$ 125,000	$ 35,000
Trade receivables sold, limit increasing fees			1,545
Service fee percentage			0.50%
Receivables outstanding in facility as of March 31:	182,856	53,156
Beneficial interest as of March 31	25,864	15,797
Servicing Liability as of March 31	45	0
Cash purchase price	638,975	405,982
Deferred purchase price	274,194	240,989
Service fees	562	504
Cash proceeds for the twelve months ended March 31: Total	$ 913,731	$ 647,475