Fair Value Measurements (Aggregate Fair Value of Derivative Financial Instruments And Debt) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Quoted Prices In Active Markets For Identical Assets/Liabilities (Level 1) [Member]
Assets:
Foreign exchange contracts		$ 0	$ 0
Pension plan assets		5,260	4,420
Total assets in fair value hierarchy		5,260	4,420
Liabilities:
Debt		35,685	29,756
Foreign exchange contracts		0	0
Total liabilities		35,685	29,756
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Foreign exchange contracts		140	813
Pension plan assets		2,028	1,740
Total assets in fair value hierarchy		2,168	2,553
Liabilities:
Debt		171	436
Foreign exchange contracts		1,128	163
Total liabilities		1,299	599
Fair Value, Inputs, Level 3 [Member]
Assets:
Foreign exchange contracts		0	0
Pension plan assets		0	0
Total assets in fair value hierarchy		0	0
Liabilities:
Debt		0	0
Foreign exchange contracts		0	0
Total liabilities		0	0
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets:
Foreign exchange contracts		140	813
Pension plan assets		7,288	6,160
Total assets in fair value hierarchy		7,428	6,973
Pension plan assets measured at net asset value	[1]	310	297
Total assets in fair value hierarchy		7,738	7,270
Liabilities:
Debt		35,856	30,192
Foreign exchange contracts		1,128	163
Total liabilities		$ 36,984	$ 30,355

[1] In accordance with FASB ASC Subtopic 820-10, certain investments measured at fair value using the net asset value per share practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in these tables are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position.