Financial Instruments - Interest Rate Swaps (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Notional	$ 12,223	$ 11,734
1.00% Euro denominated notes due 2028
Derivative [Line Items]
Interest rate	1.00%	1.00%
0.250% Euro denominated notes due 2022
Derivative [Line Items]
Interest rate	0.25%	0.25%
2.00% Euro denominated notes due 2023
Derivative [Line Items]
Interest rate	2.00%	2.00%
3.875% Euro denominated notes due 2021
Derivative [Line Items]
Interest rate	3.875%	3.875%
5.875% GBP denominated notes due 2023
Derivative [Line Items]
Interest rate	5.875%	5.875%
1.75% Euro denominated notes due 2019
Derivative [Line Items]
Interest rate	1.75%	1.75%
1.75% Euro denominated notes due 2020
Derivative [Line Items]
Interest rate	1.75%	1.75%
1.875% Euro denominated notes due 2024
Derivative [Line Items]
Interest rate	1.875%	1.875%
Designated as Hedging Instrument
Derivative [Line Items]
Derivative Notional	$ 3,107	$ 2,322
Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Derivative Notional	2,130	2,164
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap
Derivative [Line Items]
Derivative Notional	2,130	2,164
Change in Fair Value	$ 34	$ 14
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 1.00% Euro denominated notes due 2028
Derivative [Line Items]
Interest rate	1.00%	1.00%
Derivative Notional	$ 505	$ 516
Change in Fair Value	$ 24	$ 8
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 0.250% Euro denominated notes due 2022
Derivative [Line Items]
Interest rate	0.25%	0.25%
Derivative Notional	$ 337	$ 344
Change in Fair Value	$ 2	$ 2
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 2.00% Euro denominated notes due 2023
Derivative [Line Items]
Interest rate	2.00%	2.00%
Derivative Notional	$ 280	$ 287
Change in Fair Value	$ 4	$ 2
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 3.875% Euro denominated notes due 2021
Derivative [Line Items]
Interest rate	3.875%	3.875%
Derivative Notional	$ 281	$ 287
Change in Fair Value	$ 1	$ 1
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 5.875% GBP denominated notes due 2023
Derivative [Line Items]
Interest rate	5.875%	5.875%
Derivative Notional	$ 261	$ 254
Change in Fair Value	$ 3	$ 1
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 1.75% Euro denominated notes due 2019
Derivative [Line Items]
Interest rate	1.75%	1.75%
Derivative Notional	$ 225	$ 229
Change in Fair Value	$ (2)	$ (1)
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 1.75% Euro denominated notes due 2020
Derivative [Line Items]
Interest rate	1.75%	1.75%
Derivative Notional	$ 129	$ 132
Change in Fair Value	$ 0	$ 0
Designated as Hedging Instrument \| Fair Value Hedging \| Interest Rate Swap \| 1.875% Euro denominated notes due 2024
Derivative [Line Items]
Interest rate	1.875%	1.875%
Derivative Notional	$ 112	$ 115
Change in Fair Value	$ 2	$ 1

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

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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.

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No definition available.

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- Definition

Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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