Leases and Aircraft Maintenance Deposits - Leases Lease Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Finance lease cost
Amortization of leased assets	$ 998
Interest of lease liabilities	674
Operating lease cost
Operating lease cost	179,959
Short-term lease cost	5,144
Variable lease cost	140,417
Total lease cost	$ 327,192
Weighted-Average Remaining Lease Term [Abstract]
Operating leases	13 years
Finance leases	1 month 6 days
Weighted-Average Lease Discount Rate [Abstract]
Operating leases	5.86%
Finance leases	2.46%