Fair value measurement - Fair Value of Financial Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Assets:
Available-for-sale securities:	$ 9,237	$ 10,404
Equity securities	3,985	4,514
Derivatives:
Total assets	13,447	15,063
Derivatives:
Contingent consideration obligations	96	96	$ 273	$ 270
Total liabilities	1,168	1,188
Foreign currency forward contracts
Derivatives:
Derivative assets	225	145
Derivatives:
Derivative liabilities	43	116
Cross-currency swap contracts
Derivatives:
Derivative liabilities	429	405
Interest rate swap contracts
Derivatives:
Interest rate swap contracts	600	571
Quoted prices in active markets  for identical assets (Level 1)
Assets:
Equity securities	3,985	4,514
Derivatives:
Total assets	13,084	14,780
Derivatives:
Contingent consideration obligations	0	0
Total liabilities	0	0
Quoted prices in active markets  for identical assets (Level 1) | Foreign currency forward contracts
Derivatives:
Derivative assets	0	0
Derivatives:
Derivative liabilities	0	0
Quoted prices in active markets  for identical assets (Level 1) | Cross-currency swap contracts
Derivatives:
Derivative liabilities	0	0
Quoted prices in active markets  for identical assets (Level 1) | Interest rate swap contracts
Derivatives:
Interest rate swap contracts	0	0
Significant other observable inputs (Level 2)
Assets:
Equity securities	0	0
Derivatives:
Total assets	363	283
Derivatives:
Contingent consideration obligations	0	0
Total liabilities	1,072	1,092
Significant other observable inputs (Level 2) | Foreign currency forward contracts
Derivatives:
Derivative assets	225	145
Derivatives:
Derivative liabilities	43	116
Significant other observable inputs (Level 2) | Cross-currency swap contracts
Derivatives:
Derivative liabilities	429	405
Significant other observable inputs (Level 2) | Interest rate swap contracts
Derivatives:
Interest rate swap contracts	600	571
Significant unobservable inputs (Level 3)
Assets:
Equity securities	0	0
Derivatives:
Total assets	0	0
Derivatives:
Contingent consideration obligations	96	96
Total liabilities	96	96
Significant unobservable inputs (Level 3) | Foreign currency forward contracts
Derivatives:
Derivative assets	0	0
Derivatives:
Derivative liabilities	0	0
Significant unobservable inputs (Level 3) | Cross-currency swap contracts
Derivatives:
Derivative liabilities	0	0
Significant unobservable inputs (Level 3) | Interest rate swap contracts
Derivatives:
Interest rate swap contracts	0	0
Money market mutual funds
Assets:
Available-for-sale securities:	9,099	10,266
Money market mutual funds | Quoted prices in active markets  for identical assets (Level 1)
Assets:
Available-for-sale securities:	9,099	10,266
Money market mutual funds | Significant other observable inputs (Level 2)
Assets:
Available-for-sale securities:	0	0
Money market mutual funds | Significant unobservable inputs (Level 3)
Assets:
Available-for-sale securities:	0	0
Other short-term interest-bearing securities
Assets:
Available-for-sale securities:	138	138
Other short-term interest-bearing securities | Quoted prices in active markets  for identical assets (Level 1)
Assets:
Available-for-sale securities:	0	0
Other short-term interest-bearing securities | Significant other observable inputs (Level 2)
Assets:
Available-for-sale securities:	138	138
Other short-term interest-bearing securities | Significant unobservable inputs (Level 3)
Assets:
Available-for-sale securities:	$ 0	$ 0