Fair value measurement - Schedule of Fair Value of Financial Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Assets:
Available-for-sale securities:	$ 7,486	$ 11,486
Equity securities	4,898	4,188
Derivatives:
Total assets	12,493	16,094
Derivatives:
Contingent consideration obligations	90	106
Total liabilities	1,109	1,128
Foreign currency forward contracts
Derivatives:
Foreign currency forward contracts	55	420
Derivatives:
Derivative liabilities	382	8
Cross-currency swap contracts
Derivatives:
Foreign currency forward contracts	54
Derivatives:
Derivative liabilities	293	483
Interest rate swap contracts
Derivatives:
Interest rate swap contracts	344	531
Quoted prices in active markets  for identical assets (Level 1)
Assets:
Equity securities	4,898	4,188
Derivatives:
Total assets	11,261	14,542
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:
Foreign currency forward contracts	0	0
Derivatives:
Derivative liabilities	0	0
Quoted prices in active markets  for identical assets (Level 1) | Cross-currency swap contracts
Derivatives:
Foreign currency forward contracts	0
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	1,232	1,552
Derivatives:
Contingent consideration obligations	0	0
Total liabilities	1,019	1,022
Significant other observable inputs (Level 2) | Foreign currency forward contracts
Derivatives:
Foreign currency forward contracts	55	420
Derivatives:
Derivative liabilities	382	8
Significant other observable inputs (Level 2) | Cross-currency swap contracts
Derivatives:
Foreign currency forward contracts	54
Derivatives:
Derivative liabilities	293	483
Significant other observable inputs (Level 2) | Interest rate swap contracts
Derivatives:
Interest rate swap contracts	344	531
Significant unobservable inputs (Level 3)
Assets:
Equity securities	0	0
Derivatives:
Total assets	0	0
Derivatives:
Contingent consideration obligations	90	106
Total liabilities	90	106
Significant unobservable inputs (Level 3) | Foreign currency forward contracts
Derivatives:
Foreign currency forward contracts	0	0
Derivatives:
Derivative liabilities	0	0
Significant unobservable inputs (Level 3) | Cross-currency swap contracts
Derivatives:
Foreign currency forward contracts	0
Derivatives:
Derivative liabilities	0	0
Significant unobservable inputs (Level 3) | Interest rate swap contracts
Derivatives:
Interest rate swap contracts	0	0
U.S. Treasury bills
Assets:
Available-for-sale securities:	994	997
U.S. Treasury bills | Quoted prices in active markets  for identical assets (Level 1)
Assets:
Available-for-sale securities:	0	0
U.S. Treasury bills | Significant other observable inputs (Level 2)
Assets:
Available-for-sale securities:	994	997
U.S. Treasury bills | Significant unobservable inputs (Level 3)
Assets:
Available-for-sale securities:	0	0
Money market mutual funds
Assets:
Available-for-sale securities:	6,363	10,354
Money market mutual funds | Quoted prices in active markets  for identical assets (Level 1)
Assets:
Available-for-sale securities:	6,363	10,354
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:	129	135
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:	129	135
Other short-term interest-bearing securities | Significant unobservable inputs (Level 3)
Assets:
Available-for-sale securities:	$ 0	$ 0