INCOME TAXES - Deferred Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 1,217	$ 1,395
Capital loss carryforward	8	50
Pension, postretirement and other benefits	1,488	1,467
Investments	806	1,106
Deferred revenue	2,110	2,334
Lease liabilities	2,193	2,376
Other	709	682
Valuation allowance	(877)	(1,176)	$ (833)
Total deferred tax assets	7,654	8,234
Deferred tax liabilities:
Depreciation	5,570	5,110
Operating lease assets	1,533	1,624
Intangible assets	1,143	1,121
Other	73	78
Total deferred tax liabilities	8,319	7,933
Deferred income taxes, net	243	325
Deferred income taxes, net	(908)	(24)
Net deferred tax (liabilities) assets	$ (665)
Net deferred tax (liabilities) assets		$ 301