| **Finance Receivables, Net (Credit Quality Indicator) (Details) (USD $)In Millions, unless otherwise specified** | Mar. 31, 2014 | Mar. 31, 2013 |
|------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Current                                                                                                          | $ 65,180      | $ 62,593      |  |
| 30-59 Days Past Due                                                                                              | 469           | 460           |  |
| 60-89 Days Past Due                                                                                              | 92            | 88            |  |
| 90 Days or Greater Past Due                                                                                      | 33            | 31            |  |
| Total Finance Receivables                                                                                        | 65,774        | 63,172        |  |
| Wholesale [Member]                                                                                               |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Current                                                                                                          | 9,436         | 8,689         |  |
| 30-59 Days Past Due                                                                                              | 0             | 0             |  |
| 60-89 Days Past Due                                                                                              | 0             | 0             |  |
| 90 Days or Greater Past Due                                                                                      | 0             | 0             |  |
| Total Finance Receivables                                                                                        | 9,436         | 8,689         | [1] |
| Wholesale [Member] | Performing [Member]                                                                         |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 8,129         | 7,740         | [1] |
| Wholesale [Member] | Credit Watch [Member]                                                                       |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 1,282         | 915           | [1] |
| Wholesale [Member] | At Risk [Member]                                                                            |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 24            | 33            | [1] |
| Wholesale [Member] | Default [Member]                                                                            |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 1             | 1             | [1] |
| Real estate [Member]                                                                                             |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Current                                                                                                          | 4,653         | 4,580         |  |
| 30-59 Days Past Due                                                                                              | 4             | 0             |  |
| 60-89 Days Past Due                                                                                              | 1             | 0             |  |
| 90 Days or Greater Past Due                                                                                      | 0             | 0             |  |
| Total Finance Receivables                                                                                        | 4,658         | 4,580         |  |
| Real estate [Member] | Performing [Member]                                                                       |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 3,791         | 3,968         |  |
| Real estate [Member] | Credit Watch [Member]                                                                     |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 855           | 583           |  |
| Real estate [Member] | At Risk [Member]                                                                          |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 12            | 28            |  |
| Real estate [Member] | Default [Member]                                                                          |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 0             | 1             |  |
| Working capital [Member]                                                                                         |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Current                                                                                                          | 1,831         | 1,726         |  |
| 30-59 Days Past Due                                                                                              | 0             | 0             |  |
| 60-89 Days Past Due                                                                                              | 0             | 0             |  |
| 90 Days or Greater Past Due                                                                                      | 0             | 0             |  |
| Total Finance Receivables                                                                                        | 1,831         | 1,726         |  |
| Working capital [Member] | Performing [Member]                                                                   |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 1,642         | 1,616         |  |
| Working capital [Member] | Credit Watch [Member]                                                                 |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 158           | 80            |  |
| Working capital [Member] | At Risk [Member]                                                                      |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 25            | 28            |  |
| Working capital [Member] | Default [Member]                                                                      |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Total Finance Receivables                                                                                        | 6             | 2             |  |
| Retail Loan [Member]                                                                                             |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Current                                                                                                          | 48,828        | 47,236        |  |
| 30-59 Days Past Due                                                                                              | 459           | 454           |  |
| 60-89 Days Past Due                                                                                              | 90            | 87            |  |
| 90 Days or Greater Past Due                                                                                      | 33            | 31            |  |
| Total Finance Receivables                                                                                        | 49,410        | 47,808        |  |
| Commercial [Member]                                                                                              |          |          |  |
| **Financing Receivable, Recorded Investment [Line Items]**                                                       |          |          |  |
| Current                                                                                                          | 432           | 362           |  |
| 30-59 Days Past Due                                                                                              | 6             | 6             |  |
| 60-89 Days Past Due                                                                                              | 1             | 1             |  |
| 90 Days or Greater Past Due                                                                                      | 0             | 0             |  |
| Total Finance Receivables                                                                                        | $ 439         | $ 369         |  |
|                                                                                                                  |
| [1]Certain prior period amounts have been reclassified to conform to the current period presentation.            |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are less than 60 days past due but more than 29 days past due.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are less than 90 days past due but more than 59 days past due.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are current.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are equal to or greater than 90 days past due.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524
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| X                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10(3)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Subparagraph 3 -Article 9
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