Revenue Recognition - Disaggregation Of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Operating revenue	$ 75,982	$ 755,151	$ 695,130	$ 2,124,091
Passenger revenue, excluding frequent flyer
Disaggregation of Revenue [Line Items]
Operating revenue	34,623	653,424	534,926	1,834,853
Frequent flyer revenue, transportation component
Disaggregation of Revenue [Line Items]
Operating revenue	5,154	40,839	38,082	114,137
Passenger Revenue
Disaggregation of Revenue [Line Items]
Operating revenue	39,777	694,263	573,008	1,948,990
Other revenue (e.g., cargo and other miscellaneous)
Disaggregation of Revenue [Line Items]
Operating revenue	23,265	37,725	74,884	110,527
Frequent flyer revenue, marketing and brand component
Disaggregation of Revenue [Line Items]
Operating revenue	12,940	23,163	47,238	64,574
Other Revenue
Disaggregation of Revenue [Line Items]
Operating revenue	36,205	60,888	122,122	175,101
Domestic
Disaggregation of Revenue [Line Items]
Operating revenue	69,838	533,235	526,958	1,542,480
Pacific
Disaggregation of Revenue [Line Items]
Operating revenue	$ 6,144	$ 221,916	$ 168,172	$ 581,611