Long-Term Debt - Summary of Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt, gross	$ 9,308	$ 8,539
Unamortized premium (discount) and debt issuance cost, net	60	(99)
Total debt	9,368	8,440
Less: current maturities	(1,409)	(2,145)
Total long-term debt	7,959	6,295
Pacific Term Loan B-1 \| Term Loan
Debt Instrument [Line Items]
Debt, gross	0	1,048
Pacific Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt, gross	0	0
2015 Term Loan Facility \| Term Loan
Debt Instrument [Line Items]
Debt, gross	0	490
2015 Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt, gross	$ 0	0
Financings secured by aircraft - Certificates \| Secured Debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2019
Maturity dates range, end	Dec. 31, 2027
Debt, gross	$ 1,837	2,380
Financings secured by aircraft - Certificates \| Secured Debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	3.63%
Financings secured by aircraft - Certificates \| Secured Debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	8.02%
Financings secured by aircraft - Notes \| Secured Debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2019
Maturity dates range, end	Dec. 31, 2025
Debt, gross	$ 1,787	1,961
Financings secured by aircraft - Notes \| Secured Debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	2.91%
Financings secured by aircraft - Notes \| Secured Debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	6.54%
2018 Unsecured Notes \| Unsecured Debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2021
Maturity dates range, end	Dec. 31, 2028
Debt, gross	$ 1,600	0
2018 Unsecured Notes \| Unsecured Debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	3.40%
2018 Unsecured Notes \| Unsecured Debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	4.38%
2018 Revolving Credit Facility \| Unsecured Debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2021
Maturity dates range, end	Dec. 31, 2023
Debt, gross	$ 0	0
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	0
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 unsecured notes \| Unsecured Debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2020
Maturity dates range, end	Dec. 31, 2022
Debt, gross	$ 2,450	2,450
Other unsecured notes \| Unsecured Debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	2.60%
Other unsecured notes \| Unsecured Debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	3.63%
Other financings
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2019
Maturity dates range, end	Dec. 31, 2030
Other financings \| Secured and Unsecured Debt
Debt Instrument [Line Items]
Debt, gross	$ 251	210
Other financings \| Secured and Unsecured Debt \| Minimum
Debt Instrument [Line Items]
Interest rate per annum (percent)	1.81%
Other financings \| Secured and Unsecured Debt \| Maximum
Debt Instrument [Line Items]
Interest rate per annum (percent)	8.75%
Other revolving credit facilities \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt, gross	$ 0	$ 0
Other revolving credit facilities \| Secured and Unsecured Debt
Debt Instrument [Line Items]
Maturity dates range, start	Jan. 01, 2019
Maturity dates range, end	Dec. 31, 2021

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

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Latest date the outstanding debt instruments are required to be repaid, in CCYY-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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