v3.26.3
Employee Benefits - Additional Information (Detail) - USD ($)
$ in Millions
 1 Months Ended 3 Months Ended 9 Months Ended
Mar. 31, 2026
Sep. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Defined Benefit Plan Disclosure [Line Items]              
Collective-bargaining agreement, term 4 years            
Other comprehensive (income) loss, defined benefit plan, prior service cost (credit), after tax     $ (451)        
Other comprehensive income (loss), pension and other postretirement benefit plans, plan amendments, tax effect     151        
Remeasurement gain (loss), net     237        
Defined benefit plan, benefit obligation, actuarial gain (loss) from assumptions used calculating benefit obligation, discount rate     412        
Defined benefit plan, benefit obligation, actuarial gain (loss) from actuarial assumption adjustments     (175)        
Employee Severance              
Defined Benefit Plan Disclosure [Line Items]              
Amount paid in severance benefits over the period   $ 272     $ 1,400    
Post employment benefits liability   679     679    
Pension              
Defined Benefit Plan Disclosure [Line Items]              
Employer discretionary contribution amount   0     0 $ 563  
Defined benefit plan, benefit obligation, increase for plan amendment     $ 546        
Remeasurement gain (loss), net   0   $ 31 18 (14)  
Defined benefit plan, assumptions used calculating benefit obligation, discount rate 5.90%   5.90%       5.70%
Other Postretirement Benefits Plan              
Defined Benefit Plan Disclosure [Line Items]              
Defined benefit plan, benefit obligation, increase for plan amendment     $ 56        
Remeasurement gain (loss), net   $ 0   $ 0 $ 219 $ 0  
Defined benefit plan, assumptions used calculating benefit obligation, discount rate 5.70%   5.70%       5.40%