Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total short-term debt	$ 14,810	$ 11,429
Notes payable after one year	70,991	86,473
Unamortized discount	29	30
Unamortized debt issuance costs	(212)	(252)
Fair value adjustments	390	1,467
Total long-term debt	102,907	126,248
Total debt	117,717	137,677
Debt Carrying Value Fair Value	$ 37,500	$ 45,500
Average Contractual (interest rate)	2.40%	2.60%
Average Effective (interest rate)	2.40%	2.60%
Fair value of short-term debt	$ 14,100	$ 10,400
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	2,800	3,400	$ 4,100
Discontinued Hedged Debt	257	299
Fixed Interest Rate [Member]
Debt Instrument [Line Items]
Notes payable after one year	60,411	71,515
Variable Interest Rate [Member]
Debt Instrument [Line Items]
Notes payable after one year	10,580	14,958
Floating Rate Demand Notes [Member]
Debt Instrument [Line Items]
Total short-term debt	9,400	6,458
Other short-term debt [Member]
Debt Instrument [Line Items]
Total short-term debt	4,701	3,940
Asset-backed Securities [Member]
Debt Instrument [Line Items]
Total short-term debt	709	1,031
Notes payable within one year	18,049	21,345
Notes payable after one year	26,654	$ 32,276
Total debt	$ 45,412
Total short-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	1.20%	1.50%
Average Effective (interest rate)	1.30%	1.60%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Notes payable within one year	$ 13,660	$ 17,185
Notes payable after one year	44,337	$ 54,197
Total debt	$ 72,098
Total long-term debt [Member]
Debt Instrument [Line Items]
Average Contractual (interest rate)	2.60%	2.70%
Average Effective (interest rate)	2.60%	2.70%
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Fair value of debt	$ 120,204	$ 139,796