Income Taxes Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Postretirement benefits other than pensions	$ 1,948	$ 2,720
Pension and other employee benefit plans	3,285	5,141
Warranties, dealer and customer allowances, claims and discounts	5,675	8,074
Property, plant and equipment	0	397
Miscellaneous	1,697	1,733
Total deferred tax assets before valuation allowances	30,699	37,585
Less: valuation allowances	(6,690)	(3,908)
Total deferred tax assets	24,009	33,677
Deferred tax liabilities
Property, plant and equipment	418	0
Intangible assets	735	1,027
Total deferred tax liabilities	1,153	1,027
Net deferred tax assets	22,856	32,650
Change in valuation allowances	2,712	237	$ (3,554)
Discontinued Operations [Member] | Opel/Vauxhall Business [Member]
Deferred tax liabilities
Change in valuation allowances	2,300
U.S. [Member]
Deferred tax assets
U.S. capitalized research expenditures	4,413	6,127
Operating loss and tax credit carryforwards	8,578	8,987
Deferred tax liabilities
Operating loss and tax credit carryforwards subject to expiration	8,600
Non-U.S. [Member]
Deferred tax assets
Operating loss and tax credit carryforwards	5,103	4,406
Deferred tax liabilities
Operating loss and tax credit carryforwards subject to expiration	925
Operating loss and tax credit carryforwards not subject to expiration	4,200
Germany, Spain and South Korea [Member]
Deferred tax assets
Less: valuation allowances	$ (6,700)
Spain, South Korea and Certain U.S. States [Member]
Deferred tax assets
Less: valuation allowances		$ (3,900)