Allowance for Credit Losses - Aging of Finance Receivables by Class (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 475	$ 469
60-89 Days Past Due	102	92
90 Days or Greater Past Due	51	33
Total Past Due	628	594
Current	65,939	65,180
Total Finance Receivables	66,567us-gaap_NotesReceivableGross	65,774us-gaap_NotesReceivableGross
90 Days or Greater Past Due and Accruing	32	33
Retail Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	467	459
60-89 Days Past Due	100	90
90 Days or Greater Past Due	51	33
Total Past Due	618	582
Current	49,684	48,828
Total Finance Receivables	50,302	49,410
90 Days or Greater Past Due and Accruing	32	33
Commercial Finance [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	8	6
60-89 Days Past Due	2	1
90 Days or Greater Past Due	0	0
Total Past Due	10	7
Current	511	432
Total Finance Receivables	521	439
90 Days or Greater Past Due and Accruing	0
Wholesale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or Greater Past Due	0	0
Total Past Due	0	0
Current	9,226	9,436
Total Finance Receivables	9,226	9,436
90 Days or Greater Past Due and Accruing	0
Real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	4
60-89 Days Past Due	0	1
90 Days or Greater Past Due	0	0
Total Past Due	0	5
Current	4,665	4,653
Total Finance Receivables	4,665	4,658
90 Days or Greater Past Due and Accruing	0
Working capital [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or Greater Past Due	0	0
Total Past Due	0	0
Current	1,853	1,831
Total Finance Receivables	1,853	1,831
90 Days or Greater Past Due and Accruing	$ 0

Financing receivables that are less than 60 days past due but more than 29 days past due.

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=35738203&loc=SL6953401-111524

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Financing receivables that are less than 90 days past due but more than 59 days past due.

+ References

+ Details

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- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524

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- Definition

Financing receivables that are current.

+ References

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Period Type:	instant

- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

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Namespace Prefix:	us-gaap_
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Period Type:	duration

- 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=d3e534808-122878

Reference 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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