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Special Charges and Unrealized (Gains) Losses on Investments - Narrative (Details)	1 Months Ended	3 Months Ended									12 Months Ended
	May 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($) Employee	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Special Charges [Line Items]
Write-off of unexercised aircraft purchase											$ 18,000,000
Other miscellaneous impairments											20,000,000
Severance and benefit costs		$ 2,000,000	$ 2,000,000	$ 6,000,000	$ 6,000,000	$ 7,000,000	$ 9,000,000	$ 11,000,000	$ 14,000,000		16,000,000	$ 41,000,000	$ 116,000,000
Charge related to a contract termination											25,000,000
Charge for the settlement of certain legal matters											18,000,000
Gain (loss) on the sale and disposition of assets											(14,000,000)		(11,000,000)
Other charges											2,000,000		12,000,000
Gains due to the change in fair value of derivatives											13,000,000
Gain on change in market value of equity investments												28,000,000
Fair value adjustments related to aircraft purchased off lease, write-off of unexercised aircraft purchase options and other impairments												66,000,000
Termination of an engine maintenance service agreement						64,000,000	0	0	0		0	64,000,000	0
Losses due to the change in fair value of derivatives												33,000,000
Impairment of assets		102,000,000	$ 0	$ 61,000,000	$ 8,000,000	$ 232,000,000	$ 11,000,000	$ 111,000,000	$ 23,000,000		171,000,000	377,000,000	25,000,000
Weather-related damages													12,000,000
Aircraft Engines
Special Charges [Line Items]
Impairment of assets removed from operations											43,000,000
Obsolete Spare Parts Inventory
Special Charges [Line Items]
Impairment of assets													10,000,000
Maintenance Service Agreement
Special Charges [Line Items]
Intangible assets impairment charge													15,000,000
Management Reorganization Initiative
Special Charges [Line Items]
Severance and benefit costs													33,000,000
International Brotherhood of Teamsters
Special Charges [Line Items]
Severance and benefit costs											2,000,000	22,000,000	$ 83,000,000
International Brotherhood of Teamsters \| Voluntary Early Out Program
Special Charges [Line Items]
Number of technicians and related employees electing to voluntarily separate from the Company \| Employee										1,000
Severance payment per participant										$ 100,000
Management
Special Charges [Line Items]
Severance and benefit costs											14,000,000	19,000,000
Hong Kong Routes
Special Charges [Line Items]
Intangible assets impairment charge		$ 90,000,000										$ 206,000,000
Brazil Routes
Special Charges [Line Items]
Intangible assets impairment charge	$ 105,000,000
Azul
Special Charges [Line Items]
Gain on change in market value of equity investments											$ 140,000,000