v3.25.3
POSTRETIREMENT BENEFIT PLANS - Effect on Operations of Pension Plans (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Principal pension        
Defined Benefit Plan Disclosure [Line Items]        
Service cost – operating $ 6 $ 6 $ 17 $ 20
Interest cost 140 137 420 411
Expected return on plan assets (178) (186) (535) (557)
Amortization of net loss (gain) (50) (46) (149) (138)
Amortization of prior service cost (credit) 0 2 0 5
Curtailment/settlement loss (gain) 0 0 0 0
Non-operating benefit costs (income) (88) (93) (263) (279)
Net periodic expense (income) (82) (87) (246) (260)
Other pension        
Defined Benefit Plan Disclosure [Line Items]        
Service cost – operating 7 8 21 24
Interest cost 58 57 169 170
Expected return on plan assets (82) (84) (237) (250)
Amortization of net loss (gain) 10 8 30 24
Amortization of prior service cost (credit) (2) (2) (6) (5)
Curtailment/settlement loss (gain) 0 0 1 (11)
Non-operating benefit costs (income) (16) (21) (44) (71)
Net periodic expense (income) (8) (13) (22) (47)
Principal retiree benefit        
Defined Benefit Plan Disclosure [Line Items]        
Service cost – operating 1 1 4 4
Interest cost 10 9 29 28
Expected return on plan assets 0 0 0 0
Amortization of net loss (gain) (10) (11) (29) (32)
Amortization of prior service cost (credit) (14) (15) (41) (45)
Curtailment/settlement loss (gain) (1) 0 (1) 0
Non-operating benefit costs (income) (14) (16) (41) (49)
Net periodic expense (income) $ (13) $ (15) $ (37) $ (44)