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Financial Instruments - Information About Changes in Liabilities for Contingent Consideration (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 767	$ 788
Changes in estimated fair value	33	(36)
Payments	(106)	(85)
Fair value, ending balance	694	667
Current liability			$ 119
Contingent consideration	694	$ 667	694	$ 767
Sanofi Pasteur
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	625
Fair value, ending balance	520
Contingent consideration	$ 625		$ 520	$ 625
Contingent consideration, measurement input, discount rate (as percent)				0.115
Measurement Input, Discount Rate | Sanofi Pasteur
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration, measurement input, discount rate (as percent)				0.08

X

- Definition

Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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Amount of liability recognized arising from contingent consideration in a business combination.

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Value of input used to measure contingent consideration liability from business combination.

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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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