Special Charges - Narrative (Details)	1 Months Ended	3 Months Ended								12 Months Ended
	May 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) Contract	Dec. 31, 2016 USD ($)	Dec. 31, 2014 USD ($)
Special Charges [Line Items]
Fair value adjustments related to aircraft purchased off lease, write-off of unexercised aircraft purchase options and other impairments										$ 66,000,000
Fair value adjustments related to aircraft purchased off lease, write-off of unexercised aircraft purchase options and other impairments, net of tax										51,000,000
Termination of an engine maintenance service agreement		$ 64,000,000	$ 0	$ 0	$ 0					64,000,000	$ 0	$ 0
Termination of an engine maintenance service agreement, net of tax										50,000,000
Severance and benefit costs		7,000,000	9,000,000	11,000,000	14,000,000	$ 15,000,000	$ 23,000,000	$ 41,000,000	$ 37,000,000	41,000,000	116,000,000	37,000,000
Gain on change in market value of equity investments										28,000,000
Gain on change in market value of equity investments, net of tax										22,000,000
Losses due to the change in fair value of derivatives										33,000,000
Losses due to the change in fair value of derivatives, net of tax										26,000,000
Impairment of assets		232,000,000	$ 11,000,000	$ 111,000,000	$ 23,000,000	$ 10,000,000	15,000,000	$ 0	0	377,000,000	25,000,000	412,000,000
Cleveland airport lease restructuring										0	0	74,000,000
Cleveland airport lease restructuring, net of taxes												47,000,000
Labor agreement costs										0	0	171,000,000
Curtailment gain recognition of prior service credit										0	0	107,000,000
Postretirement Medical Plan | Flight Attendant Postretirement Medical Plan
Special Charges [Line Items]
Curtailment gain recognition of prior service credit												47,000,000
Curtailment gain recognition of prior service credit, net of tax												30,000,000
Newark Liberty International Airport
Special Charges [Line Items]
Impairment of indefinite-lived intangible assets											412,000,000
Impairment of indefinite-lived intangible assets, net of tax benefits											264,000,000
Voluntary Early Out Program
Special Charges [Line Items]
Severance and benefit costs												37,000,000
Severance and benefits costs, net of tax												24,000,000
Obsolete Spare Parts Inventory
Special Charges [Line Items]
Impairment of assets											10,000,000
Impairment of assets, net of tax											6,000,000
Maintenance Service Agreement
Special Charges [Line Items]
Intangible assets impairment charge							15,000,000
Intangible assets impairment charge, net of tax							$ 10,000,000
Management Reorganization Initiative
Special Charges [Line Items]
Severance and benefit costs											33,000,000
Severance and benefits costs, net of tax											21,000,000
International Brotherhood of Teamsters
Special Charges [Line Items]
Severance and benefit costs										22,000,000	83,000,000
Severance and benefits costs, net of tax										17,000,000	$ 53,000,000
International Brotherhood of Teamsters | Maximum | Voluntary Early Out Program
Special Charges [Line Items]
Severance payment per participant									$ 100,000				$ 100,000
Int'l Association of Machinists
Special Charges [Line Items]
Number of new contracts extended | Contract											7
Service contract extended year											2021
Labor agreement costs												171,000,000
Labor agreement costs, net of tax												110,000,000
Curtailment gain recognition of prior service credit												60,000,000
Curtailment gain recognition of prior service credit, net of tax												$ 38,000,000
Management
Special Charges [Line Items]
Severance and benefit costs										19,000,000
Severance and benefits costs, net of tax										$ 15,000,000
Hong Kong Routes
Special Charges [Line Items]
Intangible assets impairment charge		206,000,000
Intangible assets impairment charge, net of tax		$ 160,000,000
Brazil Routes
Special Charges [Line Items]
Intangible assets impairment charge	$ 105,000,000
Intangible assets impairment charge, net of tax	$ 82,000,000