Finance Receivables - Allowance for Loan Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201613Member
Retail Finance Receivables [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for retail loan losses beginning balance	$ 2,044	$ 881	$ 866	$ 844
Provision for loan losses	31	149	819	492
Charge-offs	(280)	(300)	(876)	(886)
Recoveries	133	133	378	410
Foreign currency translation	8	(7)	(52)	(4)
Allowance for retail loan losses ending balance	$ 1,936	$ 856	1,936	$ 856
Retail Finance Receivables [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for retail loan losses beginning balance			$ 801