Stockholders' Equity and Noncontrolling Interests Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ (9,330)
Other comprehensive income (loss), net of tax	1,317	$ (1,353)	$ 56
Balance at end of period	(8,011)	(9,330)
Foreign currency translation adjustments [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(2,355)	(2,034)	(1,064)
Other comprehensive income (loss) before reclassification adjustment, net of tax	560	(317)	(1,168)
Reclassification adjustment, net of tax	189	(4)	198
Other comprehensive income (loss), net of tax	749	(321)	(970)
Balance at end of period	(1,606)	(2,355)	(2,034)
Defined benefit plans attributable [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(6,968)	(5,999)	(7,006)
Other comprehensive income (loss) before reclassification adjustment	(798)	(1,546)	813
Tax expense (benefit)	(98)	(459)	41
Other comprehensive income (loss) before reclassification adjustment, net of tax	(700)	(1,087)	772
Reclassification adjustment, net of tax	1,270	118	235
Other comprehensive income (loss), net of tax	570	(969)	1,007
Balance at end of period	(6,398)	$ (6,968)	$ (5,999)
Defined benefit plans attributable [Member] | Discontinued Operations [Member] | Opel/Vauxhall Business [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Reclassification adjustment, net of tax	$ 1,200