v3.25.3
Fair Value Measurements - Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Assets    
Treasury bills   $ 1,094
Fuel derivatives:    
Equity Securities $ 433 367
Total assets 3,451 9,222
Option contracts    
Fuel derivatives:    
Option contracts   130
Certificates of deposit    
Assets    
Certificates of deposit 16 122
Time deposits    
Assets    
Certificates of deposit 100  
Cash equivalents    
Assets    
Cash equivalents 2,552 7,209
Time deposits    
Assets    
Cash equivalents 350 300
Quoted prices in active markets for identical assets (Level 1)    
Assets    
Treasury bills   1,094
Fuel derivatives:    
Equity Securities 433 367
Total assets 2,985 8,670
Quoted prices in active markets for identical assets (Level 1) | Option contracts    
Fuel derivatives:    
Option contracts   0
Quoted prices in active markets for identical assets (Level 1) | Certificates of deposit    
Assets    
Certificates of deposit 0 0
Quoted prices in active markets for identical assets (Level 1) | Time deposits    
Assets    
Certificates of deposit 0  
Quoted prices in active markets for identical assets (Level 1) | Cash equivalents    
Assets    
Cash equivalents 2,552 7,209
Quoted prices in active markets for identical assets (Level 1) | Time deposits    
Assets    
Cash equivalents 0 0
Significant other observable inputs (Level 2)    
Assets    
Treasury bills   0
Fuel derivatives:    
Equity Securities 0 0
Total assets 466 422
Significant other observable inputs (Level 2) | Option contracts    
Fuel derivatives:    
Option contracts   0
Significant other observable inputs (Level 2) | Certificates of deposit    
Assets    
Certificates of deposit 16 122
Significant other observable inputs (Level 2) | Time deposits    
Assets    
Certificates of deposit 100  
Significant other observable inputs (Level 2) | Cash equivalents    
Assets    
Cash equivalents 0 0
Significant other observable inputs (Level 2) | Time deposits    
Assets    
Cash equivalents $ 350 300
Significant unobservable inputs (Level 3)    
Assets    
Treasury bills   0
Fuel derivatives:    
Equity Securities   0
Total assets   130
Significant unobservable inputs (Level 3) | Option contracts    
Fuel derivatives:    
Option contracts   130
Significant unobservable inputs (Level 3) | Certificates of deposit    
Assets    
Certificates of deposit   0
Significant unobservable inputs (Level 3) | Cash equivalents    
Assets    
Cash equivalents   0
Significant unobservable inputs (Level 3) | Time deposits    
Assets    
Cash equivalents   $ 0