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Fair Value Instruments - Carrying and Estimated Fair Value of Debt (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Debt Instrument [Line Items] |  |
Debt and Capital Lease Obligations | $ 3,693 | $ 3,410
5.125% Notes due 2017 |  |
Debt Instrument [Line Items] |  |
Unsecured Debt - Carrying Value | $ 0 | 301
Interest rate stated in the debt agreement (in hundredths) | 5.125% |
French Credit Agreements due 2018 - 2.54% |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | $ 1 | 14
Interest rate stated in the debt agreement (in hundredths) | 2.54% |
Fixed-rate 737 Aircraft Notes payable through 2018 - 7.03% |  |
Debt Instrument [Line Items] |  |
Interest rate stated in the debt agreement (in hundredths) | 7.03% |
2.75% Unsecured Senior Notes Due 2019 |  |
Debt Instrument [Line Items] |  |
Unsecured Debt - Carrying Value | $ 300 | 301
Interest rate stated in the debt agreement (in hundredths) | 2.75% |
2.75% Unsecured Senior Notes Due 2019 | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Interest rate stated in the debt agreement (in hundredths) | 2.75% |
Term Loan Agreement payable through 2019 - 6.315% |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | $ 66 | 106
Interest rate stated in the debt agreement (in hundredths) | 6.315% |
Term Loan Agreement payable through 2019 - 6.315% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Interest rate stated in the debt agreement (in hundredths) | 6.315% |
Term Loan Agreement payable through 2019 - 4.84% |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | $ 19 | 28
Interest rate stated in the debt agreement (in hundredths) | 4.84% |
2.65% Notes due 2020 |  |
Debt Instrument [Line Items] |  |
Unsecured Debt - Carrying Value | $ 491 | 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 | $ 237 | 284
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% |
Term Loan Agreement Due 2021 - 7.94% |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | $ 0 | 20
Interest rate stated in the debt agreement (in hundredths) | 7.94% |
Unsecured Senior Notes Due 2022 - 2.75% |  |
Debt Instrument [Line Items] |  |
Unsecured Debt - Carrying Value | $ 300 | 0
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 | $ 294 | 324
Interest rate stated in the debt agreement (in hundredths) | 6.24% |
Term Loan Agreement Due 2026 - 2.67% |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | $ 215 | 215
Interest rate stated in the debt agreement (in hundredths) | 2.67% |
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 | 0
Interest rate stated in the debt agreement (in hundredths) | 3.45% |
7.375% Debentures due 2027 |  |
Debt Instrument [Line Items] |  |
Unsecured Debt - Carrying Value | $ 127 | 130
Interest rate stated in the debt agreement (in hundredths) | 7.375% |
Level 2 | 2.75% Unsecured Senior Notes Due 2019 | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | $ 302 |
Level 2 | 2.65% Notes due 2020 | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 494 |
Level 2 | Unsecured Senior Notes Due 2022 - 2.75% | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 300 |
Level 2 | Pass Through Certificates due 2022 - 6.24% | Enhanced Equipment Trust Certificate |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 318 |
Level 2 | Unsecured Senior Notes Due 2026 - 3.00% | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 293 |
Level 2 | Unsecured Senior Notes Due 2027 - 3.45% | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 299 |
Level 2 | 7.375% Debentures due 2027 | Unsecured Debt |  |
Debt Instrument [Line Items] |  |
Loans Payable, Fair Value | 154 |
Level 3 | French Credit Agreements due 2018 - 2.54% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 1 |
Level 3 | Fixed-rate 737 Aircraft Notes payable through 2018 - 7.03% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 3 |
Level 3 | Term Loan Agreement payable through 2019 - 6.315% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Loans Payable, Fair Value | 66 |
Level 3 | Term Loan Agreement payable through 2019 - 4.84% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 20 |
Level 3 | Term Loan Agreement payable through 2020 - 5.223% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Loans Payable, Fair Value | 240 |
Level 3 | 737 Aircraft Notes payable through 2020 | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Notes Payable, Fair Value | 154 |
Level 3 | Term Loan Agreement Due 2026 - 2.67% | Notes Payable to Banks |  |
Debt Instrument [Line Items] |  |
Loans Payable, Fair Value | 215 |
AirTran Airways | Fixed-rate 737 Aircraft Notes payable through 2018 - 7.03% |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | 3 | 8
AirTran Airways | 737 Aircraft Notes payable through 2020 |  |
Debt Instrument [Line Items] |  |
Secured Debt - Carrying Value | $ 155 | $ 206

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- Definition Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13,16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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