FINANCING ACTIVITIES - Schedule of Long-term Debt (Details) - USD ($) $ in Millions	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	$ 459	$ 542
Debt and lease obligation	10,756	10,381
Less current maturities	(453)	(220)
Less debt discount and issuance costs	29	50
Long-term debt less current maturities	10,274	10,111
Convertible Notes
Debt Instrument [Line Items]
Principal amount	$ 2,097	2,300
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	$ 300	300
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	$ 71	137
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	$ 1,250	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	$ 1,842	$ 1,945
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	$ 1,550	$ 1,550	$ 300
Term Loan Agreement payable through 2025 | Notes Payable to Banks
Debt Instrument [Line Items]
Principal amount	$ 0	119
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
Term Loan Agreement Due 2026 - 3.03% | Notes Payable to Banks
Debt Instrument [Line Items]
Principal amount	$ 0	159
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	$ 2,000	$ 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	$ 116	119
Term Loan Agreement payable through 2028 | Notes Payable to Banks
Debt Instrument [Line Items]
Principal amount	0	184
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	0
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	$ 0