Summary Of Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011
Asset-Backed Securitization Programs [Line Items]
Other current assets	$ 1,363,132,000		$ 1,363,132,000		$ 1,125,809,000
Depreciation expense associated with property and equipment	106,200,000	104,800,000	314,000,000	296,100,000
Total intangible amortization expense	13,932,000	16,571,000	41,774,000	56,000,000
Global And North American Asset-Backed Securitization Programs [Member]
Asset-Backed Securitization Programs [Line Items]
Other current assets	$ 750,300,000		$ 750,300,000		$ 460,000,000