Fair value measurement - (Fair Value of Financial Assets and Liabilities on Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets:
Interest-bearing securities	$ 9,845	$ 8,234
Equity securities	477	303
Derivatives:
Total assets	10,671	9,086
Derivatives:
Contingent consideration obligations	33	61
Total liabilities	603	407
Foreign currency contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	28	224
Derivatives:
Foreign currency and cross-currency swap contracts	237	31
Cross-currency swap contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	255	66
Derivatives:
Foreign currency and cross-currency swap contracts	318	315
Interest rate swap contracts [Member]
Derivatives:
Interest rate swap contracts	66	259
Derivatives:
Interest rate swap contracts	15	0
U.S. Treasury notes [Member]
Assets:
Interest-bearing securities	130	360
U.S. Treasury bills [Member]
Assets:
Interest-bearing securities	4,948	0
Corporate debt securities - Financial [Member]
Assets:
Interest-bearing securities	0	1,121
Corporate debt securities - Industrial [Member]
Assets:
Interest-bearing securities	0	834
Corporate debt securities - Other [Member]
Assets:
Interest-bearing securities	0	198
Residential mortgage-backed securities [Member]
Assets:
Interest-bearing securities	0	182
Money market mutual funds [Member]
Assets:
Interest-bearing securities	4,765	5,250
Other short-term interest-bearing securities [Member]
Assets:
Interest-bearing securities	2	289
Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Equity securities	477	303
Derivatives:
Total assets	10,320	5,913
Derivatives:
Contingent consideration obligations	0	0
Total liabilities	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Foreign currency contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Cross-currency swap contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Interest rate swap contracts [Member]
Derivatives:
Interest rate swap contracts	0	0
Derivatives:
Interest rate swap contracts	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| U.S. Treasury notes [Member]
Assets:
Interest-bearing securities	130	360
Quoted prices in active markets for identical assets (Level 1) [Member] \| U.S. Treasury bills [Member]
Assets:
Interest-bearing securities	4,948	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Corporate debt securities - Financial [Member]
Assets:
Interest-bearing securities	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Corporate debt securities - Industrial [Member]
Assets:
Interest-bearing securities	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Corporate debt securities - Other [Member]
Assets:
Interest-bearing securities	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Residential mortgage-backed securities [Member]
Assets:
Interest-bearing securities	0	0
Quoted prices in active markets for identical assets (Level 1) [Member] \| Money market mutual funds [Member]
Assets:
Interest-bearing securities	4,765	5,250
Quoted prices in active markets for identical assets (Level 1) [Member] \| Other short-term interest-bearing securities [Member]
Assets:
Interest-bearing securities	0	0
Significant other observable inputs (Level 2) [Member]
Assets:
Equity securities	0	0
Derivatives:
Total assets	351	3,173
Derivatives:
Contingent consideration obligations	0	0
Total liabilities	570	346
Significant other observable inputs (Level 2) [Member] \| Foreign currency contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	28	224
Derivatives:
Foreign currency and cross-currency swap contracts	237	31
Significant other observable inputs (Level 2) [Member] \| Cross-currency swap contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	255	66
Derivatives:
Foreign currency and cross-currency swap contracts	318	315
Significant other observable inputs (Level 2) [Member] \| Interest rate swap contracts [Member]
Derivatives:
Interest rate swap contracts	66	259
Derivatives:
Interest rate swap contracts	15	0
Significant other observable inputs (Level 2) [Member] \| U.S. Treasury notes [Member]
Assets:
Interest-bearing securities	0	0
Significant other observable inputs (Level 2) [Member] \| U.S. Treasury bills [Member]
Assets:
Interest-bearing securities	0	0
Significant other observable inputs (Level 2) [Member] \| Corporate debt securities - Financial [Member]
Assets:
Interest-bearing securities	0	1,121
Significant other observable inputs (Level 2) [Member] \| Corporate debt securities - Industrial [Member]
Assets:
Interest-bearing securities	0	834
Significant other observable inputs (Level 2) [Member] \| Corporate debt securities - Other [Member]
Assets:
Interest-bearing securities	0	198
Significant other observable inputs (Level 2) [Member] \| Residential mortgage-backed securities [Member]
Assets:
Interest-bearing securities	0	182
Significant other observable inputs (Level 2) [Member] \| Money market mutual funds [Member]
Assets:
Interest-bearing securities	0	0
Significant other observable inputs (Level 2) [Member] \| Other short-term interest-bearing securities [Member]
Assets:
Interest-bearing securities	2	289
Significant unobservable inputs (Level 3) [Member]
Assets:
Equity securities	0	0
Derivatives:
Total assets		0
Derivatives:
Contingent consideration obligations	33	61
Total liabilities	33	61
Significant unobservable inputs (Level 3) [Member] \| Foreign currency contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Significant unobservable inputs (Level 3) [Member] \| Cross-currency swap contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Derivatives:
Foreign currency and cross-currency swap contracts	0	0
Significant unobservable inputs (Level 3) [Member] \| Interest rate swap contracts [Member]
Derivatives:
Interest rate swap contracts	0	0
Derivatives:
Interest rate swap contracts	0	0
Significant unobservable inputs (Level 3) [Member] \| U.S. Treasury notes [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| U.S. Treasury bills [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| Corporate debt securities - Financial [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| Corporate debt securities - Industrial [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| Corporate debt securities - Other [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| Residential mortgage-backed securities [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| Money market mutual funds [Member]
Assets:
Interest-bearing securities	0	0
Significant unobservable inputs (Level 3) [Member] \| Other short-term interest-bearing securities [Member]
Assets:
Interest-bearing securities	$ 0	$ 0

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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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