v3.26.3
Fair value measurements (Assets, Measured At Fair Value Using Significant Unobservable Inputs) (Details) - Level 3 - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Equity Securities        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance- Beginning of Period, Assets $ 110 $ 125 $ 119 $ 120
Transfers Into Level 3, Asset 0 0 0 0
Transfers out of Level 3, Assets 0 0 (13) (1)
Change in Net Unrealized Gains (Losses) included in OCI, Assets 0 0 0 0
Net Realized Gains/ (Losses), Assets 1 (2) 0 (5)
Purchases, Assets 6 6 18 32
Sales, Assets (2) (15) (9) (32)
Settlements, Assets 0 0 0 0
Balance-End of Period, Assets 115 114 115 114
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets 2 4 0 13
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 $ 10 $ 42 $ 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 (1) 0 (3) 0
Net Realized Gains/ (Losses), Assets (1) 0 (1) 0
Purchases, Assets 9 2 20 32
Sales, Assets 0 (1) 0 (1)
Settlements, Assets (2) (1) (46) (3)
Balance-End of Period, Assets 15 42 15 42
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets 5 0 (1) 0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ (1) $ 0 $ (2) $ 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 $ 694 $ 598 $ 671 $ 604
Transfers Into Level 3, Asset 0 0 2 11
Transfers out of Level 3, Assets 0 (1) (2) (1)
Change in Net Unrealized Gains (Losses) included in OCI, Assets 6 3 (6) 41
Net Realized Gains/ (Losses), Assets (4) 1 (4) (2)
Purchases, Assets 83 66 193 210
Sales, Assets (33) (22) (72) (109)
Settlements, Assets (33) (43) (69) (152)
Balance-End of Period, Assets 713 602 713 602
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets (2) 0 (3) (1)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ 7 $ 1 $ (5) $ 31
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 $ 3,542 $ 3,186 $ 3,546 $ 2,891
Transfers Into Level 3, Asset 1 90 17 174
Transfers out of Level 3, Assets (1) (3) (22) (16)
Change in Net Unrealized Gains (Losses) included in OCI, Assets (19) 5 (44) (2)
Net Realized Gains/ (Losses), Assets (9) (8) (27) (14)
Purchases, Assets 321 212 731 726
Sales, Assets (71) (124) (125) (224)
Settlements, Assets (124) (119) (436) (296)
Balance-End of Period, Assets 3,640 3,239 3,640 3,239
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets 4 1 (14) (3)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ (23) $ (1) $ (55) $ (18)
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 $ 0   $ 0 $ 3
Transfers Into Level 3, Asset 18   18 0
Transfers out of Level 3, Assets 0   0 0
Change in Net Unrealized Gains (Losses) included in OCI, Assets (2)   (2) 0
Net Realized Gains/ (Losses), Assets 0   0 (2)
Purchases, Assets 96   96 1
Sales, Assets 0   0 (2)
Settlements, Assets 0   0 0
Balance-End of Period, Assets 112 $ 0 112 0
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets 0   0 0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets $ (2)   $ (2) $ 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
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues   Revenues Revenues
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Revenues   Revenues Revenues