v3.26.3
Long-term Debt, Short-term Borrowings and Finance Lease Obligations - Narrative (Details) - USD ($)
9 Months Ended
Apr. 01, 2026
Sep. 30, 2026
Sep. 30, 2025
Apr. 14, 2026
Dec. 31, 2025
Dec. 30, 2025
Line of Credit Facility [Line Items]            
Repayment of long-term debt and finance lease obligations   $ (658,000,000) $ (339,000,000)      
Pledged assets not separately reported flight equipment   8,000,000,000.0        
Long-term debt   8,393,000,000     $ 8,498,000,000  
Morgan stanley | Revolving credit facility and letter of credit facility | Line of credit            
Line of Credit Facility [Line Items]            
Line of credit facility, maximum borrowing capacity   200,000,000        
Short-term debt   $ 0     $ 0  
0.50% convertible senior notes, due through 2026            
Line of Credit Facility [Line Items]            
Debt instrument, interest rate, stated percentage (in percent) 0.50% 0.50%     0.50%  
Debt extinguished $ 325,000,000          
Interest extinguished 1,000,000          
Long-term debt $ 0 $ 0     $ 325,000,000  
Fixed rate equipment notes            
Line of Credit Facility [Line Items]            
Debt instrument, face amount       $ 500,000,000    
Secured debt   500,000,000        
Additional debt instrument       $ 250,000,000    
Second amended and restated agreement | Line of credit | Citibank            
Line of Credit Facility [Line Items]            
Line of credit facility, maximum borrowing capacity   600,000,000        
Escrow deposit           $ 100,000,000
Long-term line of credit   $ 0     $ 0