Debt (Maturities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Mar. 31, 2012
Debt [Abstract]
Total debt	$ 76,674	$ 73,234

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

No definition available.

Name:	us-gaap_DebtLongtermAndShorttermCombinedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant