Debt - Summary of Debt (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt, gross	$ 27,522	$ 28,214
Unamortized (discount)/premium and debt issue cost, net and other	(257)	(240)
Total debt	27,265	27,974
Less: current maturities	(2,019)	(1,443)
Total long-term debt	$ 25,246	26,531
Unsecured notes \| Unsecured debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2022
Maturity dates range, end	Dec. 31, 2029
Debt, gross	$ 4,750	5,350
Unsecured notes \| Unsecured debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	2.90%
Unsecured notes \| Unsecured debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	7.38%
Unsecured Payroll Support Program Loan \| Unsecured debt
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2030
Interest rate per annum (percent)	1.00%
Debt, gross	$ 1,648	1,648
Unsecured Payroll Support Program Extension Loan \| Unsecured debt
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2031
Interest rate per annum (percent)	1.00%
Debt, gross	$ 957	0
Unsecured Payroll Support Program 3 Loan \| Unsecured debt
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2031
Interest rate per annum (percent)	1.00%
Debt, gross	$ 891	0
SkyMiles Notes \| Secured debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2023
Maturity dates range, end	Dec. 31, 2028
Debt, gross	$ 6,000	6,000
SkyMiles Notes \| Secured debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	4.50%
SkyMiles Notes \| Secured debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	4.75%
SkyMiles Term Loan \| Secured debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2023
Maturity dates range, end	Dec. 31, 2027
Interest rate per annum (percent)	4.75%
Debt, gross	$ 3,000	3,000
2020 Senior Secured Notes \| Secured debt
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2025
Interest rate per annum (percent)	7.00%
Debt, gross	$ 3,500	3,500
2020 Term Loan \| Secured debt
Debt Instrument [Line Items]
Debt, gross	$ 0	1,493
2018 Revolving Credit Facility \| Revolving credit facility
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2022
Maturity dates range, end	Dec. 31, 2023
Debt, gross	$ 0	0
Financing secured by aircraft - Certificates \| Secured debt
Debt Instrument [Line Items]
Maturity dates range, start	Jul. 01, 2021
Maturity dates range, end	Dec. 31, 2028
Debt, gross	$ 2,009	2,633
Financing secured by aircraft - Certificates \| Secured debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	2.00%
Financing secured by aircraft - Certificates \| Secured debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	8.00%
Financing secured by aircraft - Notes \| Secured debt
Debt Instrument [Line Items]
Maturity dates range, start	Jul. 01, 2021
Maturity dates range, end	Dec. 31, 2033
Debt, gross	$ 1,279	1,284
Financing secured by aircraft - Notes \| Secured debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	0.71%
Financing secured by aircraft - Notes \| Secured debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	5.75%
NYTDC Special Facilities Revenue Bonds, Series 2020 \| Bonds
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2026
Maturity dates range, end	Dec. 31, 2045
Debt, gross	$ 1,511	1,511
NYTDC Special Facilities Revenue Bonds, Series 2020 \| Bonds \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	4.00%
NYTDC Special Facilities Revenue Bonds, Series 2020 \| Bonds \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	5.00%
NYTDC Special Facilities Revenue Bonds, Series 2018 \| Bonds
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2022
Maturity dates range, end	Dec. 31, 2036
Debt, gross	$ 1,383	1,383
NYTDC Special Facilities Revenue Bonds, Series 2018 \| Bonds \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	4.00%
NYTDC Special Facilities Revenue Bonds, Series 2018 \| Bonds \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	5.00%
Other financings \| Secured and unsecured debt
Debt Instrument [Line Items]
Maturity dates range, start	Jul. 01, 2021
Maturity dates range, end	Dec. 31, 2030
Debt, gross	$ 594	412
Other financings \| Secured and unsecured debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	2.25%
Other financings \| Secured and unsecured debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	8.00%
Other revolving credit facilities \| Revolving credit facility
Debt Instrument [Line Items]
Maturity date	Dec. 31, 2022
Debt, gross	$ 0	$ 0

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

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Latest date the outstanding debt instruments are required to be repaid, in YYYY-MM-DD format.

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Earliest date the outstanding debt instruments are required to be repaid, in YYYY-MM-DD format.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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