Fair Value Measurements And Disclosure (Long-Term Debt And Other Financial Instruments) (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Carrying Amount [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Notes and debentures	[1]	$ 170,532	$ 171,529
Commercial paper		2,957	3,048
Bank borrowings		4	4
Investment securities	[2]	3,606	3,409
Fair Value [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Commercial paper		2,957	3,048
Bank borrowings		4	4
Investment securities	[2]	3,606	3,409
Fair Value [Member] | Level 2 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Notes and debentures	[1]	$ 179,576	$ 172,287

[1] Includes credit agreement borrowings.

[2] Excludes investments accounted for under the equity method.