Debt (Details) (USD $)	3 Months Ended	12 Months Ended
Dec. 31, 2014	Mar. 31, 2014
Debt Instrument [Line Items]
Debt	$ 87,954,000,000	$ 85,367,000,000
Weighted average contractual interest rate	1.22%us-gaap_DebtWeightedAverageInterestRate	1.26%us-gaap_DebtWeightedAverageInterestRate
Commercial paper [Member]
Debt Instrument [Line Items]
Debt	27,485,000,000	27,709,000,000
Weighted average contractual interest rate	0.19%	0.18%
Commercial paper average remaining maturity	As of December 31, 2014, our commercial paper had a weighted average remaining maturity of 80 days.
Unsecured notes and loans payable [Member]
Debt Instrument [Line Items]
Debt	51,029,000,000	49,075,000,000
Weighted average contractual interest rate	1.90%	1.99%
Debt denominated in foreign currency	11,300,000,000	12,600,000,000
Unsecured notes and loans payable [Member] \| Floating rate [Member]
Debt Instrument [Line Items]
Debt	17,600,000,000	17,600,000,000
Contractual interest rate, minimum	0.00%	0.00%
Contractual interest rate, maximum	3.30%	3.30%
Unsecured notes and loans payable [Member] \| Fixed rate [Member]
Debt Instrument [Line Items]
Debt	33,600,000,000	31,900,000,000
Contractual interest rate, minimum	0.50%	0.50%
Contractual interest rate, maximum	9.40%	9.40%
Secured notes and loans payable [Member]
Debt Instrument [Line Items]
Debt	9,335,000,000	8,158,000,000
Weighted average contractual interest rate	0.57%	0.54%
Debt maturity dates	As of December 31, 2014, our notes and loans payable mature on various dates through fiscal 2047.
Secured notes and loans payable [Member] \| Floating rate [Member]
Debt Instrument [Line Items]
Contractual interest rate, minimum	0.40%	0.40%
Contractual interest rate, maximum	1.50%	1.60%
Secured notes and loans payable [Member] \| Fixed rate [Member]
Debt Instrument [Line Items]
Contractual interest rate, minimum	0.40%	0.40%
Contractual interest rate, maximum	1.50%	1.60%
Carrying value adjustment [Member]
Debt Instrument [Line Items]
Debt	$ 105,000,000	$ 425,000,000

Portion of a debt instrument that is denominated in foreign currency.

No definition available.

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- Definition

Maximum contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Minimum contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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- Definition

Disclosure of timing of required repayments, sinking fund requirements, and other redeemable securities at fixed or determinable prices and dates in the five years immediately following the date of the latest balance sheet presented in the financial statements, and the amount thereafter to fully repay the principal of long-term debt. These disclosures may be made either on an individual debt or security basis, by type of debt or security basis, or on a combined basis.

+ References

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- Definition

Description of the short-term debt arrangement, and disclosures pertaining to the underlying arrangements, including repayment terms, interest rates, restrictions on assets and activities, debt covenants, and other matters important to users of the financial statements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph b

-Article 5

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