Fair Value Instruments - Carrying and Estimated Fair Value of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt and Lease Obligation	$ 2,678	$ 3,396
2.75% Unsecured Senior Notes Due November 2019
Debt Instrument [Line Items]
Unsecured Debt - Carrying Value	$ 0	300
Interest rate stated in the debt agreement (in hundredths)	2.75%
Term Loan Agreement payable through May 2019 - 6.315%
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 0	23
Interest rate stated in the debt agreement (in hundredths)	6.315%
Term Loan Agreement payable through July 2019 - 4.84%
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 0	10
Interest rate stated in the debt agreement (in hundredths)	4.84%
2.65% Notes due 2020
Debt Instrument [Line Items]
Unsecured Debt - Carrying Value	$ 500	492
Interest rate stated in the debt agreement (in hundredths)	2.65%
2.65% Notes due 2020 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	2.65%
Term Loan Agreement payable through 2020 - 5.223%
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 134	187
Interest rate stated in the debt agreement (in hundredths)	5.223%
Term Loan Agreement payable through 2020 - 5.223% | Notes Payable to Banks
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (in hundredths)	5.223%
Unsecured Senior Notes Due 2022 - 2.75%
Debt Instrument [Line Items]
Unsecured Debt - Carrying Value	$ 300	300
Interest rate stated in the debt agreement (in hundredths)	2.75%
Pass Through Certificates due 2022 - 6.24% | Enhanced Equipment Trust Certificate
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 197	250
Interest rate stated in the debt agreement (in hundredths)	6.24%
Term Loan Agreement Due 2026 - 3.03%
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 178	197
Interest rate stated in the debt agreement (in hundredths)	3.03%
Unsecured Senior Notes Due 2026 - 3.00%
Debt Instrument [Line Items]
Unsecured Debt - Carrying Value	$ 300	300
Interest rate stated in the debt agreement (in hundredths)	3.00%
Unsecured Senior Notes Due 2027 - 3.45%
Debt Instrument [Line Items]
Unsecured Debt - Carrying Value	$ 300	300
Interest rate stated in the debt agreement (in hundredths)	3.45%
7.375% Debentures due 2027
Debt Instrument [Line Items]
Unsecured Debt - Carrying Value	$ 122	125
Interest rate stated in the debt agreement (in hundredths)	7.375%
Level 2 | 2.65% Notes due 2020 | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	$ 503
Level 2 | Unsecured Senior Notes Due 2022 - 2.75% | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	304
Level 2 | Pass Through Certificates due 2022 - 6.24% | Enhanced Equipment Trust Certificate
Debt Instrument [Line Items]
Notes Payable, Fair Value	208
Level 2 | Unsecured Senior Notes Due 2026 - 3.00% | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	308
Level 2 | Unsecured Senior Notes Due 2027 - 3.45% | Unsecured Debt
Debt Instrument [Line Items]
Notes Payable, Fair Value	317
Level 2 | 7.375% Debentures due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Loans Payable, Fair Value	150
Level 3 | Term Loan Agreement payable through 2020 - 5.223% | Notes Payable to Banks
Debt Instrument [Line Items]
Loans Payable, Fair Value	134
Level 3 | 737 Aircraft Notes payable through 2020 | Notes Payable to Banks
Debt Instrument [Line Items]
Notes Payable, Fair Value	20
Level 3 | Term Loan Agreement Due 2026 - 3.03% | Notes Payable to Banks
Debt Instrument [Line Items]
Loans Payable, Fair Value	178
AirTran Airways | 737 Aircraft Notes payable through 2020
Debt Instrument [Line Items]
Secured Debt - Carrying Value	$ 20	$ 67