v3.26.3
RETIREMENT BENEFITS - Schedule of Defined Benefit Plans - Expense (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
OPEB        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Service cost $ 5 $ 5 $ 15 $ 15
Interest cost 49 55 148 165
Expected return on assets 0 0 0 0
Amortization of prior service costs/(credits) 2 3 7 7
Net remeasurement (gain)/loss 0 0 0 0
Separation costs/other 0 0 0 0
Settlements and curtailments 0 0 0 0
Net periodic benefit cost/(income) 56 63 170 187
U.S. Plans | Pension Benefits        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Service cost 53 53 159 157
Interest cost 352 392 1,058 1,178
Expected return on assets (448) (456) (1,346) (1,369)
Amortization of prior service costs/(credits) 22 22 66 66
Net remeasurement (gain)/loss 0 0 0 0
Separation costs/other 0 6 0 18
Settlements and curtailments 0 0 0 0
Net periodic benefit cost/(income) (21) 17 (63) 50
Non-U.S. Plans | Pension Benefits        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)        
Service cost 39 51 123 149
Interest cost 251 245 751 707
Expected return on assets (291) (297) (879) (864)
Amortization of prior service costs/(credits) 6 7 18 19
Net remeasurement (gain)/loss (320) 0 (509) (10)
Separation costs/other 12 4 75 39
Settlements and curtailments 8 0 27 0
Net periodic benefit cost/(income) $ (295) $ 10 $ (394) $ 40