FINANCING ACTIVITIES - Schedule of Long-term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jul. 31, 2020	May 04, 2020	May 01, 2020	Feb. 29, 2020	Nov. 30, 2017	Nov. 30, 2016	Feb. 28, 1997
Debt Instrument [Line Items]
Finance leases	$ 189	$ 459
Debt and lease obligation	8,111	10,756
Less current maturities	(42)	(453)
Less debt discount and issuance costs	23	29
Long-term debt less current maturities	$ 8,046	10,274
Pass Through Certificates due 2022 - 6.24% | Enhanced Equipment Trust Certificate
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	6.24%
Principal amount	$ 0	71
2.75% Notes due 2022
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)								2.75%
2.75% Notes due 2022 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	2.75%
Principal amount	$ 0	300
4.75% Notes due 2023
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					4.75%
4.75% Notes due 2023 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	4.75%
Principal amount	$ 0	1,250
1.25% Convertible Notes due 2025 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	1.25%
1.25% Convertible Notes due 2025 | Convertible Notes
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)						1.25%
Principal amount	$ 1,611	1,842
5.25% Notes due 2025 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	5.25%		5.25%
Principal amount	$ 1,302	1,550		$ 300
3.00% Notes due 2026
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)									3.00%
3.00% Notes due 2026 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	3.00%
Principal amount	$ 300	300
3.45% Notes due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	3.45%
Principal amount	$ 300	300
5.125% Notes due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	5.125%		5.125%
Principal amount	$ 1,727	2,000		$ 700
7.375% Debentures due 2027
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)										7.375%
7.375% Debentures due 2027 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	7.375%
Principal amount	$ 114	116
2.625% Notes due 2030 | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)							2.625%
Principal amount	$ 500	500
1.000% Payroll Support Program Loan due April 2030 (See Note 2) | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	1.00%
Principal amount	$ 976	976
1.000% Payroll Support Program Loan due January 2031 (See Note 2) | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	1.00%
Principal amount	$ 566	566
1.000% Payroll Support Program Loan due April 2031 (See Note 2) | Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)	1.00%
Principal amount	$ 526	$ 526