Other Liabilities and Deferred Revenue (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Accounts Payable and Accrued Liabilities, Current [Abstract]
Dealer and dealers’ customer allowances and claims	$ 8,610	$ 12,702
Deferred revenue	2,418	2,161
Employee benefit plans	1,574	1,752
Accrued interest	999	1,215
OPEB (a)	341	339
Pension (a)	193	193
Operating lease liabilities	340	323
Other	4,394	4,960
Total current other liabilities and deferred revenue	18,869	23,645
Accounts Payable and Accrued Liabilities, Noncurrent [Abstract]
Pension (a)	10,258	10,738
OPEB (a)	6,193	6,236
Dealer and dealers’ customer allowances and claims	3,470	3,072
Deferred revenue	4,649	4,559
Operating lease liabilities	969	991
Employee benefit plans	1,075	1,074
Other	1,972	1,709
Total non-current other liabilities and deferred revenue	28,586	28,379
Net pension assets	$ 5,500	$ 4,300