Debt - Narrative (Details)
1 Months Ended 5 Months Ended 12 Months Ended
Feb. 28, 2019
USD ($)
lender
Jun. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
numberOfAircraft
Oct. 31, 2019
USD ($)
2019 unsecured notes | Unsecured Debt        
Debt Instrument [Line Items]        
Debt instrument face amount       $ 1,500,000,000
2019 unsecured notes at 2.9% due 2024 | Unsecured Debt        
Debt Instrument [Line Items]        
Debt instrument face amount       $ 900,000,000
Interest rate (percent)       2.90%
2019 unsecured notes at 3.75% due 2029 | Unsecured Debt        
Debt Instrument [Line Items]        
Debt instrument face amount       $ 600,000,000
Interest rate (percent)       3.75%
Pass Through Certificates Series 2019-1 | Secured Debt        
Debt Instrument [Line Items]        
Debt instrument face amount     $ 500,000,000  
Number of aircraft used to secure loans | numberOfAircraft     14  
2019 unsecured term loan | Term Loan        
Debt Instrument [Line Items]        
Debt instrument face amount $ 1,000,000,000      
Number of lenders | lender 2      
Repayment of debt   $ 1,000,000,000