| **Debt (Tables)**                                            | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| **Debt [Abstract]**                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Debt and Related Weighted Average Contractual Interest Rates | Note 9 – Debt                        Debt and the related weighted average contractual interest rates are summarized as follows:                                  Weighted average      contractual interest rates  March 31, March 31,(Dollars in millions)2014 20132014 2013Commercial paper$ 27,709 $ 24,590  0.18%  0.24%Unsecured notes and loans payable  49,075   46,707  1.99%  2.19%Secured notes and loans payable  8,158   7,009  0.54%  0.60%Carrying value adjustment  425   526      Total debt$ 85,367 $ 78,832  1.26%  1.43%              |
| Schedule of Maturities of Long-term Debt                     |      Future Years ending March 31,    debt maturities    2015 $ 44,9442016   13,7182017   7,8872018   8,1172019   3,506Thereafter   7,195Total debt $ 85,367                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |

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| - Definition
Tabular disclosure of information pertaining to short-term and long-debt instruments or arrangements, including but not limited to identification of terms, features, collateral requirements and other information necessary to a fair presentation.
+ References
No definition available.
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| - Definition
Tabular disclosure of the combined aggregate amount of maturities and sinking fund requirements for all long-term borrowings for each of the five years following the date of the latest balance sheet date presented.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601
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