Financial Instruments (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Derivative instruments in fair value hedging relationships \| Interest rate swaps
Derivative Instruments, Gain (Loss)
Notional amount	$ 6,600	$ 5,800
Average remaining maturity	7 years 10 months	8 years 8 months
Derivative instruments in cash flow hedging relationships \| Foreign exchange forward contracts
Derivative Instruments, Gain (Loss)
Notional amount	9,300	9,300
Average remaining maturity	8 months 12 days	8 months 12 days
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	972	602
Gains (losses) expected to be reclassified to net income within the next 12 months	921	572
Maximum length of time hedged	4 years
Derivative instruments in cash flow hedging relationships \| Interest rate swaps
Derivative Instruments, Gain (Loss)
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	1	1
Derivative instruments in cash flow hedging relationships \| Interest rate swaps \| Maximum
Derivative Instruments, Gain (Loss)
Gains (losses) expected to be reclassified to net income within the next 12 months	1	1
Derivative instruments in cash flow hedging relationships \| Currency swaps
Derivative Instruments, Gain (Loss)
Notional amount	0	0
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	(2)	(2)
Maximum length of time hedged	7 years
Derivative instruments in cash flow hedging relationships \| Currency swaps \| Maximum
Derivative Instruments, Gain (Loss)
Gains (losses) expected to be reclassified to net income within the next 12 months	(1)	(1)
Derivative instruments in net investment hedging relationships
Derivative Instruments, Gain (Loss)
Notional amount	4,200	2,200
Average remaining maturity	2 months 12 days	2 months 12 days
Derivative instruments not designated as hedging instruments \| Foreign exchange forward and swap contracts
Derivative Instruments, Gain (Loss)
Notional amount	11,200	13,100
Maximum length of time hedged	1 year
Derivative instruments not designated as hedging instruments \| Equity contracts
Derivative Instruments, Gain (Loss)
Notional amount	1,200	1,300
Derivative instruments not designated as hedging instruments \| Equity options \| Maximum
Derivative Instruments, Gain (Loss)
Notional amount	$ 100	$ 100

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount before tax of increase (decrease) in accumulated in equity from transactions and other events and circumstances from non-owner sources. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners).

+ References

No definition available.

+ Details

Name:	us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

+ Details

Name:	us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAverageRemainingMaturity1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

+ Details

Name:	us-gaap_MaximumLengthOfTimeHedgedInCashFlowHedge1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_NetInvestmentHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: