Condensed Consolidated Statement of Cash Flows $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Statement of Cash Flows [Abstract]
Net income	$ 1,715	$ 1,263	$ 929
Net Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	1,555	1,649	1,859
Provision for loan losses	998	918	1,148
Gain on mortgage and automotive loans, net	(28)	(25)	(68)
Other loss (gain) on investments, net	(243)	50	(102)
Originations and purchases of loans held-for-sale	(1,276)	(1,016)	(414)
Proceeds from sales and repayments of loans held-for-sale	1,288	948	310
Increase (decrease) in deferred income taxes	179	330	534
Increase (decrease) in interest payable	118	148	24
Increase (decrease) in other assets	(28)	(87)	(153)
Increase (decrease) in other liabilities	(177)	2	(69)
Increase (decrease) in other assets and liabilities, net	(51)	(30)	81
Net cash provided by operating activities	4,050	4,150	4,079
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(498)	(1,076)	(899)
Proceeds from sales of equity securities	814	787	1,049
Purchases of available-for-sale securities	15,199	7,868	10,335
Proceeds from sales of available-for-sale securities	7,079	852	3,584
Proceeds from repayments of available-for-sale securities	5,154	3,215	2,899
Purchases of held-to-maturity securities	(514)	(578)	(1,026)
Proceeds from repayments of held-to-maturity securities	302	147	68
Purchases of finance receivables and loans held-for-investment	(4,439)	(5,693)	(5,452)
Proceeds from sales of finance receivables and loans initially held-for-investment	1,038	91	1,339
Originations and repayments of finance receivables and loans held-for-investment and other, net	4,252	(3,245)	(1,063)
Purchases of operating lease assets	(4,023)	(3,709)	(4,052)
Disposals of operating lease assets	2,625	3,089	5,567
Acquisitions, net of acquired cash	(171)	0	0
Net change in nonmarketable equity investments	190	(181)	(187)
Payments for (proceeds from) other, net	(379)	(340)	(219)
Net cash used in investing activities	(3,769)	(14,509)	(8,727)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	(4,456)	(1,426)	(1,263)
Net increase in deposits	14,547	12,867	14,172
Proceeds from issuance of long-term debt	6,915	18,401	17,969
Repayments of long-term debt	(17,224)	(17,940)	(27,908)
Repurchase of common stock	(1,039)	(939)	(753)
Dividends paid	(273)	(242)	(184)
Net cash provided by financing activities	(1,530)	10,721	2,033
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	3	(5)	3
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net increase (decrease) in cash and cash equivalents and restricted cash	(1,246)	357	(2,612)
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	5,626	5,269	7,881
Cash and cash equivalents and restricted cash	4,380	5,626	5,269
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	4,034	3,380	2,829
Cash paid for income taxes	64	36	51
Held-to-maturity securities received in consideration for loans sold	0	26	56
Loans held-for-sale transferred to finance receivables and loans held-for-investment	242	0	0
Finance receivables and loans transferred to loans held-for-sale, noncash	960	815	1,339
Held-to-maturity securities transferred to available-for-sale	943	0	$ 0
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet	3,555	4,537
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	$ 825	$ 1,089