Fair Value Measurements Summary of assets and liabilities measured at fair value (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets:
Available-for-sale debt securities	$ 25,059	$ 24,164
Total	4,351	6,310
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement
Assets:
Total	29,458	30,552
Liabilities:
Total	162	125
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| U.S. treasury securities
Assets:
Available-for-sale debt securities	3,916	3,969
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Certificates of deposit
Assets:
Available-for-sale debt securities	5,385	4,361
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	1,531	938
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	420	305
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Corporate debt securities
Assets:
Available-for-sale debt securities	13,271	13,067
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	536	1,524
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Money market funds
Assets:
Equity securities	3,007	5,305
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Publicly traded equity securities
Assets:
Equity securities	1,188	881
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Deferred compensation plan
Assets:
Equity securities	156	124
Liabilities:
Deferred compensation plan	156	124
Fair Value, Measurements, Recurring \| Estimate of Fair Value Measurement \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	48	78
Liabilities:
Foreign currency derivative contracts	6	1
Fair Value, Measurements, Recurring \| Level 1
Assets:
Total	8,251	10,279
Liabilities:
Total	156	124
Fair Value, Measurements, Recurring \| Level 1 \| U.S. treasury securities
Assets:
Available-for-sale debt securities	3,916	3,969
Fair Value, Measurements, Recurring \| Level 1 \| Certificates of deposit
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Corporate debt securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Money market funds
Assets:
Equity securities	3,007	5,305
Fair Value, Measurements, Recurring \| Level 1 \| Publicly traded equity securities
Assets:
Equity securities	1,172	881
Fair Value, Measurements, Recurring \| Level 1 \| Deferred compensation plan
Assets:
Equity securities	156	124
Liabilities:
Deferred compensation plan	156	124
Fair Value, Measurements, Recurring \| Level 1 \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Fair Value, Measurements, Recurring \| Level 2
Assets:
Total	21,207	20,273
Liabilities:
Total	6	1
Fair Value, Measurements, Recurring \| Level 2 \| U.S. treasury securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Certificates of deposit
Assets:
Available-for-sale debt securities	5,385	4,361
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	1,531	938
Fair Value, Measurements, Recurring \| Level 2 \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	420	305
Fair Value, Measurements, Recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt securities	13,271	13,067
Fair Value, Measurements, Recurring \| Level 2 \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	536	1,524
Fair Value, Measurements, Recurring \| Level 2 \| Money market funds
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Publicly traded equity securities
Assets:
Equity securities	16	0
Fair Value, Measurements, Recurring \| Level 2 \| Deferred compensation plan
Assets:
Equity securities	0	0
Liabilities:
Deferred compensation plan	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	48	78
Liabilities:
Foreign currency derivative contracts	6	1
Fair Value, Measurements, Recurring \| Level 3
Assets:
Total	0	0
Liabilities:
Total	0	0
Fair Value, Measurements, Recurring \| Level 3 \| U.S. treasury securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Certificates of deposit
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| U.S. government agencies securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Non-U.S. government securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Corporate debt securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Residential mortgage and asset-backed securities
Assets:
Available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Money market funds
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Publicly traded equity securities
Assets:
Equity securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Deferred compensation plan
Assets:
Equity securities	0	0
Liabilities:
Deferred compensation plan	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	$ 0	$ 0

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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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Fair value of financial and nonfinancial obligations.

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Fair value portion of other liabilities.

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