Other Liabilities and Deferred Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Other Liabilities [Abstract]
Dealer and Dealers' Customer Allowances and Claims	$ 12,113	$ 11,369
Deferred Revenue, Current	2,019	2,095
Deferred Compensation Liability, Current	1,590	1,755
Interest Payable, Current	838	988
Other Postretirement Defined Benefit Plan Liabilities Current	340	339
Liability, Defined Benefit Pension Plan, Current	201	204
Operating Lease, Liability, Current	335	0
Other Sundry Liabilities, Current	3,928	3,806
Other Liabilities, Current	21,364	20,556
Pension (a)	9,073	9,423
OPEB (a)	5,207	5,220
Operating lease liabilities	2,251	2,497
Deferred revenue	4,104	3,985
Operating Lease, Liability, Noncurrent	1,025	0
Employee benefit plans	1,101	1,080
Other	1,455	1,383
Total non-current other liabilities and deferred revenue	24,216	23,588
Net pension assets	$ 3,600	$ 3,300