Finance Receivables - Finance Receivables, net (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables, net	$ 52,262		$ 53,473
Level 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value utilizing inputs	7,817		12,071
Level 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value utilizing inputs	46,619		42,012
Retail Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables, net of fees	46,489		42,268
Less: allowance for loan losses	(2,044)	$ (1,879)	(866)	$ (881)	$ (862)	$ (844)
Total finance receivables, net	44,445		41,402
Deferred income	218		83
Commercial Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables, net of fees	7,884		12,149
Less: allowance for loan losses	(67)		(78)
Total finance receivables, net	7,817		12,071
Dealer cash management balances	$ 1,300		$ 1,200