Financing Activities (Details) (USD $) In Billions, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2011 years	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011
Accounts Receivable Sales Facility [Member]
Line of Credit Facility [Line Items]
Number of years for which accounts receivable sales facility was renewed	1
Credit facility		$ 1.35		$ 1.35
Credit facility expiration date				May 2012
Securitized receivable balance		0		0		0
Borrowings outstanding		0		0		0
Accounts receivable sold under the facility		0	0	0	0
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility		1.30		1.30
Credit facility expiration date				September 2016
Borrowings outstanding		0		0		0
Borrowings during the period				$ 0	$ 0