Fair value measurements Summary of assets and liabilities recorded at fair value (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Available-for-sale debt securities	$ 16,500	$ 24,164
Total	7,562	5,688
Equity investment in Galapagos
Assets
Total	3,477	622
Fair Value, Recurring [Member] \| Fair value
Assets
Total	27,576	30,552
Liabilities
Total	179	125
Fair Value, Recurring [Member] \| Fair value \| U.S. treasury securities
Assets
Available-for-sale debt securities	2,433	3,969
Fair Value, Recurring [Member] \| Fair value \| Certificates of deposit
Assets
Available-for-sale debt securities	3,517	4,361
Fair Value, Recurring [Member] \| Fair value \| U.S. government agencies securities
Assets
Available-for-sale debt securities	1,081	938
Fair Value, Recurring [Member] \| Fair value \| Non-U.S. government securities
Assets
Available-for-sale debt securities	174	305
Fair Value, Recurring [Member] \| Fair value \| Corporate debt securities
Assets
Available-for-sale debt securities	9,204	13,067
Fair Value, Recurring [Member] \| Fair value \| Residential mortgage and asset-backed securities
Assets
Available-for-sale debt securities	91	1,524
Fair Value, Recurring [Member] \| Fair value \| Equity investment in Galapagos
Assets
Marketable equity securities	3,477	622
Fair Value, Recurring [Member] \| Fair value \| Money market funds
Assets
Marketable equity securities	7,069	5,305
Fair Value, Recurring [Member] \| Fair value \| Other publicly traded equity securities
Assets
Marketable equity securities	322	259
Fair Value, Recurring [Member] \| Fair value \| Deferred compensation plan
Assets
Marketable equity securities	171	124
Liabilities
Deferred compensation plan	171	124
Fair Value, Recurring [Member] \| Fair value \| Foreign currency derivative contracts
Assets
Foreign currency derivative contracts	37	78
Liabilities
Foreign currency derivative contracts	8	1
Fair Value, Recurring [Member] \| Level 1
Assets
Total	13,472	10,279
Liabilities
Total	171	124
Fair Value, Recurring [Member] \| Level 1 \| U.S. treasury securities
Assets
Available-for-sale debt securities	2,433	3,969
Fair Value, Recurring [Member] \| Level 1 \| Certificates of deposit
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 1 \| U.S. government agencies securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 1 \| Non-U.S. government securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 1 \| Corporate debt securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 1 \| Residential mortgage and asset-backed securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 1 \| Equity investment in Galapagos
Assets
Marketable equity securities	3,477	622
Fair Value, Recurring [Member] \| Level 1 \| Money market funds
Assets
Marketable equity securities	7,069	5,305
Fair Value, Recurring [Member] \| Level 1 \| Other publicly traded equity securities
Assets
Marketable equity securities	322	259
Fair Value, Recurring [Member] \| Level 1 \| Deferred compensation plan
Assets
Marketable equity securities	171	124
Liabilities
Deferred compensation plan	171	124
Fair Value, Recurring [Member] \| Level 1 \| Foreign currency derivative contracts
Assets
Foreign currency derivative contracts	0	0
Liabilities
Foreign currency derivative contracts	0	0
Fair Value, Recurring [Member] \| Level 2
Assets
Total	14,104	20,273
Liabilities
Total	8	1
Fair Value, Recurring [Member] \| Level 2 \| U.S. treasury securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 2 \| Certificates of deposit
Assets
Available-for-sale debt securities	3,517	4,361
Fair Value, Recurring [Member] \| Level 2 \| U.S. government agencies securities
Assets
Available-for-sale debt securities	1,081	938
Fair Value, Recurring [Member] \| Level 2 \| Non-U.S. government securities
Assets
Available-for-sale debt securities	174	305
Fair Value, Recurring [Member] \| Level 2 \| Corporate debt securities
Assets
Available-for-sale debt securities	9,204	13,067
Fair Value, Recurring [Member] \| Level 2 \| Residential mortgage and asset-backed securities
Assets
Available-for-sale debt securities	91	1,524
Fair Value, Recurring [Member] \| Level 2 \| Equity investment in Galapagos
Assets
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Level 2 \| Money market funds
Assets
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Level 2 \| Other publicly traded equity securities
Assets
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Level 2 \| Deferred compensation plan
Assets
Marketable equity securities	0	0
Liabilities
Deferred compensation plan	0	0
Fair Value, Recurring [Member] \| Level 2 \| Foreign currency derivative contracts
Assets
Foreign currency derivative contracts	37	78
Liabilities
Foreign currency derivative contracts	8	1
Fair Value, Recurring [Member] \| Level 3
Assets
Total	0	0
Liabilities
Total	0	0
Fair Value, Recurring [Member] \| Level 3 \| U.S. treasury securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Certificates of deposit
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| U.S. government agencies securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Non-U.S. government securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Corporate debt securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Residential mortgage and asset-backed securities
Assets
Available-for-sale debt securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Equity investment in Galapagos
Assets
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Money market funds
Assets
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Other publicly traded equity securities
Assets
Marketable equity securities	0	0
Fair Value, Recurring [Member] \| Level 3 \| Deferred compensation plan
Assets
Marketable equity securities	0	0
Liabilities
Deferred compensation plan	0	0
Fair Value, Recurring [Member] \| Level 3 \| Foreign currency derivative contracts
Assets
Foreign currency derivative contracts	0	0
Liabilities
Foreign currency derivative contracts	$ 0	$ 0

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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