Commitments and Contingencies - Firm Commitments and Options to Purchase Aircraft (Details)	Jun. 30, 2020 commitment
Airbus A321XLR
Long-term Purchase Commitment [Line Items]
Number of firm commitments	50
Scheduled Aircraft Deliveries
Last Six Months of 2020	0
2021	0
2022	0
After 2022	50
Airbus A350
Long-term Purchase Commitment [Line Items]
Number of firm commitments	45
Scheduled Aircraft Deliveries
Last Six Months of 2020	0
2021	0
2022	0
After 2022	45
Boeing 737 MAX
Long-term Purchase Commitment [Line Items]
Number of firm commitments	171
Scheduled Aircraft Deliveries
Last Six Months of 2020	16
2021	24
2022	0
After 2022	131
Boeing 787
Long-term Purchase Commitment [Line Items]
Number of firm commitments	16
Scheduled Aircraft Deliveries
Last Six Months of 2020	8
2021	8
2022	0
After 2022	0
Embraer E175
Long-term Purchase Commitment [Line Items]
Number of firm commitments	20
Scheduled Aircraft Deliveries
Last Six Months of 2020	16
2021	4
2022	0
After 2022	0