Accumulated Other Comprehensive (Loss) Income (Components of Accumulated Other Comprehensive Income Loss) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Deferred tax asset on foreign currency translation adjustments	$ 2	$ (8)
Deferred tax asset on net charges related to pension/post-retirement plans	1,463	1,340
Components of AOCI	12,370	10,749	$ 11,222
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Components of AOCI	(5,295)	(5,314)	(4,575)	$ (5,110)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Components of AOCI	(2,194)	(2,593)	(1,373)
Pension/Post-Retirement Plans Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Components of AOCI	$ (3,101)	$ (2,721)	$ (3,202)