Commitments and Contingencies - Narrative (Details)
$ in Millions
12 Months Ended
Dec. 31, 2019
USD ($)
numberOfAircraft
MD-90 Fleet Retirement  
Future Purchase Commitments  
Accelerated depreciation related to permanent fleet retirement | $ $ 79
MD-90  
Future Purchase Commitments  
Time ahead of plan for fleet retirement (in years) 2 years
Number of aircraft permanently retired 35
A350-900 | LATAM  
Future Purchase Commitments  
Number of aircraft agreed to acquire 4
Number of aircraft commitments planned to be assumed 10