Leases - Future Minimum Rental Payment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Future minimum rental payments required under operating leases
2020	$ 94,806
2021	84,285
2022	73,960
2023	68,581
2024	27,282
Thereafter	94,746
Total	443,660
Total rental expense for non-cancelable aircraft operating leases		$ 154,900	$ 215,800
Total rental expense for non-cancelable aircraft operating leases	72,000
Minimum rental expense for airport station rents		19,600	$ 30,300
Minimum rental expense for airport station rents	$ 23,100
Future minimum rental payments required under operating leases
2019		87,256
2020		101,741
2021		90,787
2022		72,593
2023		65,749
Thereafter		59,820
Total future lease obligations		$ 477,946