Finance Receivables - Finance Receivables, net (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables, net	$ 55,153		$ 53,473
Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value utilizing inputs	8,394		12,071
Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value utilizing inputs	48,973		42,012
Retail Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables, net of fees	48,695		42,268
Less: allowance for loan losses	(1,936)	$ (2,044)	(866)	$ (856)	$ (881)	$ (844)
Total finance receivables, net	46,759		41,402
Deferred income	63		83
Commercial Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables, net of fees	8,461		12,149
Less: allowance for loan losses	(67)		(78)
Total finance receivables, net	8,394		12,071
Dealer cash management balances	$ 1,400		$ 1,200