Summary Of Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Summary Of Accounting Policies [Line Items]
Research and development costs	$ 78,900,000	$ 46,500,000	$ 13,300,000
Number of customers accounting for greater than 10% of accounts receivable	0	0
Maximum percentage of credit exposure	20.00%
Maximum amount of credit exposure	10,000,000
Other current assets	1,100,906,000	1,119,889,000
Depreciation expense associated with property and equipment	412,200,000	389,400,000	372,600,000
Intangible asset amortization expense	55,896,000	70,913,000	89,615,000
Equity investments in non-majority owned companies	38,600,000	34,000,000
Gain on sale of equity investments		18,600,000
Impairment charges to equity investments and notes receivable			199,400,000
Deferred revenue	329,600,000	110,100,000
Customer working capital advances, amount	326,600,000	296,300,000
Global And North American Asset-Backed Securitization Programs [Member]
Summary Of Accounting Policies [Line Items]
Other current assets	$ 514,900,000	$ 460,000,000
Minimum [Member]
Summary Of Accounting Policies [Line Items]
Percentage of ownership under equity method	20.00%
Maximum [Member]
Summary Of Accounting Policies [Line Items]
Minority interest for the ownership of the minority owners	100.00%
Net sales, percentage	10.00%	10.00%	10.00%
Percentage of ownership under equity method	50.00%
Customer One [Member]
Summary Of Accounting Policies [Line Items]
Net sales, percentage	11.00%
Customer Two [Member]
Summary Of Accounting Policies [Line Items]
Net sales, percentage	10.00%
Two Customers [Member]
Summary Of Accounting Policies [Line Items]
Net sales, percentage		11.00%	10.00%
Number of customers accounting for greater than 10% of net sales	2
One Customer [Member]
Summary Of Accounting Policies [Line Items]
Number of customers accounting for greater than 10% of net sales		1
Ten Largest Customers [Member]
Summary Of Accounting Policies [Line Items]
Net sales, percentage	55.00%	52.00%	47.00%
Customer Relationships [Member]
Summary Of Accounting Policies [Line Items]
Weighted-average remaining useful lives of intangible assets	1.8
Customer Relationships [Member] | Maximum [Member]
Summary Of Accounting Policies [Line Items]
Intangibles amortized on accelerated method expected cash flows, in years	8
Licenses And Other Intangible [Member]
Summary Of Accounting Policies [Line Items]
Weighted-average remaining useful lives of intangible assets	3.0
Licenses And Other Intangible [Member] | Maximum [Member]
Summary Of Accounting Policies [Line Items]
Intangibles amortized on accelerated method expected cash flows, in years	7