v3.26.1
Fair value measurements (Assets, Measured At Fair Value Using Significant Unobservable Inputs) (Details) - Level 3 - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Equity Securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance- Beginning of Period, Assets $ 121 $ 113 $ 119 $ 120
Transfers Into Level 3, Asset 0 0 0 0
Transfers out of Level 3, Assets (13) (1) (13) (1)
Change in Net Unrealized Gains (Losses) included in OCI, Assets 0 0 0 0
Net Realized Gains/ (Losses), Assets (1) 2 (1) (3)
Purchases, Assets 6 19 12 26
Sales, Assets (3) (8) (7) (17)
Settlements, Assets 0 0 0 0
Balance-End of Period, Assets 110 125 110 125
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets (2) 4 (2) 9
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ 0 $ 0 $ 0 $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Short-term Investments        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance- Beginning of Period, Assets $ 11 $ 18 $ 45 $ 14
Transfers Into Level 3, Asset 0 0 0 0
Transfers out of Level 3, Assets 0 0 0 0
Change in Net Unrealized Gains (Losses) included in OCI, Assets 0 0 (2) 0
Net Realized Gains/ (Losses), Assets 0 0 0 0
Purchases, Assets 3 25 11 30
Sales, Assets 0 0 0 0
Settlements, Assets (4) (1) (44) (2)
Balance-End of Period, Assets 10 42 10 42
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets (6) 0 (6) 0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ 0 $ 0 $ (1) $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Available-for-Sale Debt Securities | Non-U.S.        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance- Beginning of Period, Assets $ 689 $ 587 $ 671 $ 604
Transfers Into Level 3, Asset 0 10 2 11
Transfers out of Level 3, Assets (2) 0 (2) 0
Change in Net Unrealized Gains (Losses) included in OCI, Assets (2) 18 (12) 38
Net Realized Gains/ (Losses), Assets 0 3 0 (3)
Purchases, Assets 34 84 110 144
Sales, Assets (9) (34) (39) (87)
Settlements, Assets (16) (70) (36) (109)
Balance-End of Period, Assets 694 598 694 598
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets (1) 0 (1) (1)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ (2) $ 16 $ (12) $ 30
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Available-for-Sale Debt Securities | Corporate and asset-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance- Beginning of Period, Assets $ 3,536 $ 3,017 $ 3,546 $ 2,891
Transfers Into Level 3, Asset 15 60 16 84
Transfers out of Level 3, Assets (4) (12) (21) (13)
Change in Net Unrealized Gains (Losses) included in OCI, Assets (11) (3) (25) (7)
Net Realized Gains/ (Losses), Assets (11) (4) (18) (6)
Purchases, Assets 299 295 410 514
Sales, Assets (53) (53) (54) (100)
Settlements, Assets (229) (114) (312) (177)
Balance-End of Period, Assets 3,542 3,186 3,542 3,186
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets (15) (1) (18) (4)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ (14) $ (7) $ (32) $ (17)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax Other comprehensive income (loss), before income tax
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues Revenues Revenues Revenues
Available-for-Sale Debt Securities | Mortgage-backed securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance- Beginning of Period, Assets       $ 3
Transfers Into Level 3, Asset       0
Transfers out of Level 3, Assets       0
Change in Net Unrealized Gains (Losses) included in OCI, Assets       0
Net Realized Gains/ (Losses), Assets       (2)
Purchases, Assets       1
Sales, Assets       (2)
Settlements, Assets       0
Balance-End of Period, Assets   $ 0   0
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets       0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets       $ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]       Other comprehensive income (loss), before income tax
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]       Revenues
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]       Revenues