Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Air traffic liability	$ 402,990		$ 402,990		$ 291,981
Total operating revenues	1,012,956	$ 851,771	1,868,752	$ 1,555,909
DOT—Domestic [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	890,388	768,297	1,644,502	1,417,433
DOT—Latin America [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	122,568	83,474	224,250	138,476
Passenger [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	994,430	836,350	1,832,495	1,525,491
Fare [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	515,696	439,549	932,041	782,244
Non Fare [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	478,734	396,801	900,454	743,247
Other [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 18,526	$ 15,421	$ 36,257	$ 30,418