Leases, Commitments and Contingencies (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) aircraft	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 248,576		$ 248,576		$ 282,362
Current maturities of lease liabilities	78,188		78,188		82,641
Noncurrent operating leases	$ 171,443		171,443		$ 205,845
Operating leases			$ 63,100
Weighted-average remaining lease term for operating leases	6 years 3 months 18 days		6 years 3 months 18 days
Weighted-average discount rate for operating leases	6.00%		6.00%
Lease costs
Operating lease cost	$ 23,370	$ 23,538	$ 67,582	$ 72,696
Variable and short-term lease cost	976	950	3,256	3,501
Sublease income	(1,888)	(1,587)	(4,717)	(4,718)
Total lease cost	$ 22,458	$ 22,901	$ 66,121	$ 71,479
Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft leased | aircraft			43
Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	3 years		3 years
Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	9 years		9 years
Airport Facilities | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	1 month		1 month
Airport Facilities | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	35 years		35 years