Parent Company Condensed Financial Information (Condensed Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by Operating Activities	$ 3,739	$ 4,050	$ 4,150
Net Cash (Used in) Provided by Investing Activities [Abstract]
Proceeds from sales of finance receivables and loans initially held-for-investment	506	1,038	91
Originations and repayments of loans held-for-investment and other	15,353	4,252	(3,245)
Purchases of finance receivables and loans held-for-investment	(7,020)	(4,439)	(5,693)
Disposals of operating lease assets	2,681	2,625	3,089
Net change in nonmarketable equity investments	417	190	(181)
Payments for (Proceeds from) Other Investing Activities	(450)	(379)	(340)
Net Cash Provided by (Used in) Investing Activities, Total	8,427	(3,769)	(14,509)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	(3,395)	(4,456)	(1,426)
Net increase in deposits	16,262	14,547	12,867
Proceeds from issuance of long-term debt	3,660	6,915	18,401
Repayments of Long-term Debt	(16,107)	(17,224)	(17,940)
Repurchase of common stock	(106)	(1,039)	(939)
Dividends paid	(289)	(273)	(242)
Net Cash Provided by (Used in) Financing Activities, Total	25	(1,530)	10,721
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	12,194	(1,246)	357
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	4,380	5,626	5,269
Cash and cash equivalents and restricted cash	16,574	4,380	5,626
Restricted Cash [Abstract]
Cash and cash equivalents	15,621	3,555
Restricted cash included in other assets on the Consolidated Balance Sheet	953	825
Parent company
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by Operating Activities	848	1,818	1,659
Net Cash (Used in) Provided by Investing Activities [Abstract]
Proceeds from sales of finance receivables and loans initially held-for-investment	1,187	548	1,596
Originations and repayments of loans held-for-investment and other	601	(253)	3,489
Net change in loans - intercompany	(36)	718	(20)
Purchases of finance receivables and loans held-for-investment	0	0	(131)
Disposals of operating lease assets	1	3	10
Capital contributions to subsidiaries	(8)	(2)	(61)
Returns of contributed capital	23	259	266
Net change in nonmarketable equity investments	(7)	(13)	(16)
Payments for (Proceeds from) Other Investing Activities	(15)	(4)	0
Net Cash Provided by (Used in) Investing Activities, Total	1,746	1,256	5,133
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	(445)	104	(694)
Net increase in deposits	0	0	(11)
Proceeds from issuance of long-term debt	2,885	801	69
Repayments of Long-term Debt	(2,444)	(2,173)	(4,774)
Net change in debt - intercompany	169	271	(198)
Repurchase of common stock	(106)	(1,039)	(939)
Dividends paid	(290)	(273)	(242)
Net Cash Provided by (Used in) Financing Activities, Total	(231)	(2,309)	(6,789)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	2,363	765	3
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	2,163	1,398	1,395
Cash and cash equivalents and restricted cash	4,526	2,163	$ 1,398
Restricted Cash [Abstract]
Cash and cash equivalents	4,482	2,105
Restricted cash included in other assets on the Consolidated Balance Sheet	$ 44	$ 58