Income Taxes (Details) (USD $)	3 Months Ended				6 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Income Tax [Line Items]
Effective income tax rate	275.00%		30.00%		70.00%		31.00%
Federal statutory income tax rate	35.00%		35.00%		35.00%		35.00%
Charge recorded to accrue European Commission fines	$ 49,091,000	[1]	$ (7,445,000)	[1]	$ 49,091,000	[1]	$ (7,445,000)	[1]
Italy [Member] | European Commission Fine [Member]
Income Tax [Line Items]
Non-deductible portion of charge for European Commission fine	$ 40,000,000
Italy [Member] | Excluding European Commission Fine [Member]
Income Tax [Line Items]
Effective income tax rate	29.00%				31.00%

[1] Item is not included in segment operating income, but is included in consolidated operating income.