Summary of Significant Accounting Policies - Passenger Revenues (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Jul. 28, 2021	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Air traffic liability		$ 382,317				$ 401,966				$ 382,317	$ 401,966
Total operating revenues		$ 987,556	$ 922,631	$ 859,309	$ 461,279	$ 498,490	$ 401,922	$ 138,529	$ 771,081	3,230,775	$ 1,810,022	$ 3,830,536
Credit shell term of expiration	90 days											60 days
Minimum
Disaggregation of Revenue [Line Items]
Credit shell term of expiration											60 days
Maximum
Disaggregation of Revenue [Line Items]
Credit shell term of expiration											21 months
Baggage
Disaggregation of Revenue [Line Items]
Total operating revenues										663,228	$ 404,896	$ 734,243
Passenger usage fee
Disaggregation of Revenue [Line Items]
Total operating revenues										610,762	358,561	669,177
Advance seat selection
Disaggregation of Revenue [Line Items]
Total operating revenues										215,682	125,213	228,876
Other
Disaggregation of Revenue [Line Items]
Total operating revenues										263,203	120,638	238,454
Non-fare revenue
Disaggregation of Revenue [Line Items]
Total operating revenues										$ 1,752,875	$ 1,009,308	$ 1,870,750