Fair Value Measurements - Financial Assets and Liabilities Not Carried at Fair Value on Recurring Basis in Consolidated Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Carrying value [Member]
Financial liabilities
Commercial paper	$ 27,006	$ 27,709
Unsecured notes and loans payable	52,388	49,500
Secured notes and loans payable	10,837	8,158
Fair value [Member]
Financial liabilities
Commercial paper	27,006	27,709
Unsecured notes and loans payable	53,808	50,433
Secured notes and loans payable	10,832	8,165
Fair value [Member] \| Level 1 [Member]
Financial liabilities
Commercial paper	0	0
Unsecured notes and loans payable	0	0
Secured notes and loans payable	0	0
Fair value [Member] \| Level 2 [Member]
Financial liabilities
Commercial paper	27,006	27,709
Unsecured notes and loans payable	53,174	49,697
Secured notes and loans payable	0	0
Fair value [Member] \| Level 3 [Member]
Financial liabilities
Commercial paper	0	0
Unsecured notes and loans payable	634	736
Secured notes and loans payable	10,832	8,165
Retail Loan [Member] \| Carrying value [Member]
Financial assets
Finance receivables, net	49,734	48,892
Retail Loan [Member] \| Fair value [Member]
Financial assets
Finance receivables, net	49,887	49,392
Retail Loan [Member] \| Fair value [Member] \| Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Retail Loan [Member] \| Fair value [Member] \| Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Retail Loan [Member] \| Fair value [Member] \| Level 3 [Member]
Financial assets
Finance receivables, net	49,887	49,392
Commercial Finance [Member] \| Carrying value [Member]
Financial assets
Finance receivables, net	217	174
Commercial Finance [Member] \| Fair value [Member]
Financial assets
Finance receivables, net	223	160
Commercial Finance [Member] \| Fair value [Member] \| Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Commercial Finance [Member] \| Fair value [Member] \| Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Commercial Finance [Member] \| Fair value [Member] \| Level 3 [Member]
Financial assets
Finance receivables, net	223	160
Wholesale [Member] \| Carrying value [Member]
Financial assets
Finance receivables, net	9,123	9,344
Wholesale [Member] \| Fair value [Member]
Financial assets
Finance receivables, net	9,176	9,391
Wholesale [Member] \| Fair value [Member] \| Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Wholesale [Member] \| Fair value [Member] \| Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Wholesale [Member] \| Fair value [Member] \| Level 3 [Member]
Financial assets
Finance receivables, net	9,176	9,391
Real estate [Member] \| Carrying value [Member]
Financial assets
Finance receivables, net	4,602	4,601
Real estate [Member] \| Fair value [Member]
Financial assets
Finance receivables, net	4,564	4,552
Real estate [Member] \| Fair value [Member] \| Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Real estate [Member] \| Fair value [Member] \| Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Real estate [Member] \| Fair value [Member] \| Level 3 [Member]
Financial assets
Finance receivables, net	4,564	4,552
Working capital [Member] \| Carrying value [Member]
Financial assets
Finance receivables, net	1,815	1,802
Working capital [Member] \| Fair value [Member]
Financial assets
Finance receivables, net	1,804	1,807
Working capital [Member] \| Fair value [Member] \| Level 1 [Member]
Financial assets
Finance receivables, net	0	0
Working capital [Member] \| Fair value [Member] \| Level 2 [Member]
Financial assets
Finance receivables, net	0	0
Working capital [Member] \| Fair value [Member] \| Level 3 [Member]
Financial assets
Finance receivables, net	$ 1,804	$ 1,807

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents unsecured promissory note that provides creditworthy institutions with short-term funds as of the balance sheet date.

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents collateralized debt obligation (backed by pledge, mortgage or other lien on the entity's assets) as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents debt obligation not collateralized by pledge, mortgage or other lien in the entity's assets as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Glossary Loan

-URI http://asc.fasb.org/extlink&oid=6517073

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