Debt - Narrative (Details)				3 Months Ended
	Mar. 02, 2018	Aug. 23, 2017 USD ($)	Jul. 18, 2016	Mar. 31, 2020 USD ($)	Apr. 17, 2020 USD ($)	Dec. 31, 2019 USD ($)
Line of Credit Facility [Line Items]
Outstanding debt				$ 3,699,000,000		$ 3,343,000,000
Debt issuance costs				14,000,000		15,000,000
Unamortized discount				5,000,000		6,000,000
Face value of outstanding debt				3,638,291,000		3,282,195,000
Outstanding letters of credit that will reduce overall credit capacity				$ 11,000,000		12,000,000
Subsequent Event
Line of Credit Facility [Line Items]
Number of debt agreements					2
Senior Secured Notes 9.250% Due 2025 | Senior Secured Notes | Subsequent Event
Line of Credit Facility [Line Items]
Aggregate principal amount					$ 775,000,000
Interest rate					9.25%
Senior Secured Notes 4.000% Due 2025 | Senior Secured Notes | Subsequent Event
Line of Credit Facility [Line Items]
Aggregate principal amount					$ 345,000,000
Interest rate					4.00%
Amended And Restated Credit Agreement
Line of Credit Facility [Line Items]
Percent of domestic revenue passenger enplanements				10.00%
Amended And Restated Credit Agreement | Senior secured credit facilities
Line of Credit Facility [Line Items]
Total net leverage ratio			4.5
Revolving Credit Facility | Senior secured credit facilities
Line of Credit Facility [Line Items]
Face value of outstanding debt				$ 375,000,000		0
Revolving Credit Facility | Fourth Incremental Term Facility Amendment | Senior secured credit facilities
Line of Credit Facility [Line Items]
Credit facility amount		$ 400,000,000
Senior secured first-lien net leverage ratio		3.75
Revolving Credit Facility | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Eurocurrency | Minimum
Line of Credit Facility [Line Items]
Variable basis spread		2.50%
Revolving Credit Facility | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Eurocurrency | Maximum
Line of Credit Facility [Line Items]
Variable basis spread		1.75%
Revolving Credit Facility | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Base Rate | Minimum
Line of Credit Facility [Line Items]
Variable basis spread		1.50%
Revolving Credit Facility | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Base Rate | Maximum
Line of Credit Facility [Line Items]
Variable basis spread		0.75%
New Term Loan B | Senior secured credit facilities
Line of Credit Facility [Line Items]
Variable basis spread				2.00%
Face value of outstanding debt				$ 1,838,724,000		1,843,427,000
New Term Loan B | Fourth Incremental Term Facility Amendment | Senior secured credit facilities
Line of Credit Facility [Line Items]
Credit facility amount		$ 1,891,000,000
Senior secured first-lien net leverage ratio		3.00
New Term Loan B | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Eurocurrency
Line of Credit Facility [Line Items]
Variable basis spread		2.25%
New Term Loan B | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Base Rate
Line of Credit Facility [Line Items]
Variable basis spread		1.25%
New Term Loan B | Fifth Incremental Term Facility Amendment | Senior secured credit facilities | Eurocurrency
Line of Credit Facility [Line Items]
Variable basis spread	2.00%
New Term Loan B | Fifth Incremental Term Facility Amendment | Senior secured credit facilities | Base Rate
Line of Credit Facility [Line Items]
Variable basis spread	1.00%
New Term Loan A | Senior secured credit facilities
Line of Credit Facility [Line Items]
Variable basis spread				2.25%
Face value of outstanding debt				$ 470,250,000		$ 484,500,000
New Term Loan A | Fourth Incremental Term Facility Amendment | Senior secured credit facilities
Line of Credit Facility [Line Items]
Credit facility amount		$ 570,000,000
Decrease in variable basis spread, quarterly		0.25%
Decrease in variable basis spread, maximum		0.75%
Senior secured first-lien net leverage ratio		2.25
New Term Loan A | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Eurocurrency | Minimum
Line of Credit Facility [Line Items]
Variable basis spread		2.50%
New Term Loan A | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Eurocurrency | Maximum
Line of Credit Facility [Line Items]
Variable basis spread		1.75%
New Term Loan A | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Base Rate | Minimum
Line of Credit Facility [Line Items]
Variable basis spread		1.50%
New Term Loan A | Fourth Incremental Term Facility Amendment | Senior secured credit facilities | Base Rate | Maximum
Line of Credit Facility [Line Items]
Variable basis spread		0.75%