Derivative instruments (Details Textual) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Foreign currency and cross currency swap contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts expected to be reclassified from AOCI into earnings over the next 12 months, foreign currency and cross-currency swaps	$ (119)
Rate adjustment to LIBOR on interest rate swap agreements [Member] \| Three-Month LIBOR [Member] \| Minimum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, variable interest rate	0.30%
Rate adjustment to LIBOR on interest rate swap agreements [Member] \| Three-Month LIBOR [Member] \| Maximum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, variable interest rate	2.00%
Derivatives designated as hedging instrument [Member] \| Foreign currency forward contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	$ 4,800	$ 4,600
Derivatives designated as hedging instrument [Member] \| Foreign currency option contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	21	74
Derivatives designated as hedging instrument [Member] \| Interest rate swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	9,450	9,450
Derivatives not designated as hedging instrument [Member] \| Foreign currency forward contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	$ 268	$ 757

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

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- Definition

The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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- Details

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