Stockholders' Equity and Noncontrolling Interests Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period			$ 36,200	$ 44,075
Other comprehensive loss, net of tax	$ (94)	$ (118)	(67)	(39)
Balance at end of period	38,636	45,725	38,636	45,725
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period	(1,498)	(2,264)	(1,606)	(2,355)
Other comprehensive income and noncontrolling interests, net of reclassification adjustment, tax and impact of adoption of accounting standards	(328)	102	(220)	193
Balance at end of period	(1,826)	(2,162)	(1,826)	(2,162)
Defined benefit plans [Member]
Accumulated Other Comprehensive Loss, Net of Tax [Roll Forward]
Balance at beginning of period	(6,524)	(6,997)	(6,398)	(6,968)
Other comprehensive loss before reclassification adjustment, net of tax and impact of adoption of accounting standards	190	(266)	20	(343)
Reclassification adjustment, net of tax	44	55	88	103
Other comprehensive loss, net of tax	234	(211)	108	(240)
Balance at end of period	$ (6,290)	$ (7,208)	$ (6,290)	$ (7,208)