Fair value measurement (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets:
Interest-bearing securities	$ 11,589	$ 8,234
Equity securities	376	303
Derivatives:
Total assets	12,309	9,086
Derivatives:
Contingent consideration obligations	54	61
Total liabilities	627	407
Foreign currency contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	111	224
Derivatives:
Foreign currency and cross-currency swap contracts	88	31
Cross-currency swap contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	124	66
Derivatives:
Foreign currency and cross-currency swap contracts	481	315
Interest rate swap contracts [Member]
Derivatives:
Interest rate swap contracts	109	259
Derivatives:
Interest rate swap contracts	4	0
Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Equity securities	376	303
Derivatives:
Total assets	11,965	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
Significant other observable inputs (Level 2) [Member]
Assets:
Equity securities	0	0
Derivatives:
Total assets	344	3,173
Derivatives:
Contingent consideration obligations	0	0
Total liabilities	573	346
Significant other observable inputs (Level 2) [Member] | Foreign currency contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	111	224
Derivatives:
Foreign currency and cross-currency swap contracts	88	31
Significant other observable inputs (Level 2) [Member] | Cross-currency swap contracts [Member]
Derivatives:
Foreign currency and cross-currency swap contracts	124	66
Derivatives:
Foreign currency and cross-currency swap contracts	481	315
Significant other observable inputs (Level 2) [Member] | Interest rate swap contracts [Member]
Derivatives:
Interest rate swap contracts	109	259
Derivatives:
Interest rate swap contracts	4	0
Significant unobservable inputs (Level 3) [Member]
Assets:
Equity securities	0	0
Derivatives:
Total assets	0	0
Derivatives:
Contingent consideration obligations	54	61
Total liabilities	54	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
U.S. Treasury notes [Member]
Assets:
Interest-bearing securities	174	360
U.S. Treasury notes [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	174	360
U.S. Treasury notes [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	0
U.S. Treasury notes [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
U.S. Treasury bills [Member]
Assets:
Interest-bearing securities	6,399	0
U.S. Treasury bills [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	6,399	0
U.S. Treasury bills [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	0
U.S. Treasury bills [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
Corporate debt securities - Financial [Member]
Assets:
Interest-bearing securities	0	1,121
Corporate debt securities - Financial [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	0	0
Corporate debt securities - Financial [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	1,121
Corporate debt securities - Financial [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
Corporate debt securities - Industrial [Member]
Assets:
Interest-bearing securities	0	834
Corporate debt securities - Industrial [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	0	0
Corporate debt securities - Industrial [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	834
Corporate debt securities - Industrial [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
Corporate debt securities - Other [Member]
Assets:
Interest-bearing securities	0	198
Corporate debt securities - Other [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	0	0
Corporate debt securities - Other [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	198
Corporate debt securities - Other [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
Residential mortgage-backed securities [Member]
Assets:
Interest-bearing securities	0	182
Residential mortgage-backed securities [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	0	0
Residential mortgage-backed securities [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	182
Residential mortgage-backed securities [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
Money market mutual funds [Member]
Assets:
Interest-bearing securities	5,016	5,250
Money market mutual funds [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	5,016	5,250
Money market mutual funds [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	0
Money market mutual funds [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	0	0
Other short-term interest-bearing securities [Member]
Assets:
Interest-bearing securities	0	289
Other short-term interest-bearing securities [Member] | Quoted prices in active markets for identical assets (Level 1) [Member]
Assets:
Interest-bearing securities	0	0
Other short-term interest-bearing securities [Member] | Significant other observable inputs (Level 2) [Member]
Assets:
Interest-bearing securities	0	289
Other short-term interest-bearing securities [Member] | Significant unobservable inputs (Level 3) [Member]
Assets:
Interest-bearing securities	$ 0	$ 0