Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Air traffic liability	$ 361,218		$ 361,218		$ 291,981
Total operating revenues	991,968	$ 904,330	2,860,720	$ 2,460,239
DOT—Domestic [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	880,868	819,323	2,526,016	2,236,334
DOT—Latin America [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	111,100	85,007	334,704	223,905
Passenger [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	973,353	887,956	2,805,848	2,413,447
Fare [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	493,376	476,660	1,425,417	1,258,904
Non Fare [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	479,977	411,296	1,380,431	1,154,543
Other [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 18,615	$ 16,374	$ 54,872	$ 46,792