Consolidated Statement of Cash Flows $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Statement of Cash Flows [Abstract]
Net income	$ 1,085	$ 1,715	$ 1,263
Net Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	1,550	1,555	1,649
Goodwill impairment	50	0	0
Provision for credit losses	1,439	998	918
Gain on mortgage and automotive loans, net	(110)	(28)	(25)
Other (gain) loss on investments, net	(307)	(243)	50
Change in Gain (Loss) On Extinguishment Of Debt	102	2	1
Originations and purchases of loans held-for-sale	(3,199)	(1,276)	(1,016)
Proceeds from sales and repayments of loans held-for-sale	3,161	1,288	948
Increase (decrease) in deferred income taxes	242	179	330
Increase (decrease) in interest payable	(229)	118	148
Increase (decrease) in other assets	15	(28)	(87)
Increase (decrease) in other liabilities	33	(177)	2
Increase (decrease) in other assets and liabilities, net	(93)	(53)	(31)
Net Cash Provided by (Used in) Operating Activities, Total	3,739	4,050	4,150
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(1,219)	(498)	(1,076)
Proceeds from sales of equity securities	1,087	814	787
Purchases of available-for-sale securities	17,377	15,199	7,868
Proceeds from Sale of Debt Securities, Available-for-sale	6,563	7,079	852
Proceeds from repayments of available-for-sale securities	11,903	5,154	3,215
Purchases of held-to-maturity securities	(154)	(514)	(578)
Proceeds from repayments of held-to-maturity securities	457	302	147
Purchases of finance receivables and loans held-for-investment	(7,020)	(4,439)	(5,693)
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 operating lease assets	(4,320)	(4,023)	(3,709)
Disposals of operating lease assets	2,681	2,625	3,089
Payments to Acquire Businesses, Net of Cash Acquired	0	(171)	0
Net change in nonmarketable equity investments	417	190	(181)
Payments for (proceeds from) other, net	(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
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations	3	3	(5)
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, Total	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
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	3,366	4,034	3,380
Cash paid for income taxes	53	64	36
Held-to-maturity securities received in consideration for loans sold	0	0	26
Loans held-for-sale transferred to finance receivables and loans held-for-investment	75	242	0
Finance receivables and loans transferred to loans held-for-sale, noncash	495	960	815
Debt Securities, Held-to-maturity, Transfer, Amount	0	943	0
In-kind distribution from equity method investee	226	0	0
Equity consideration received in exchange for restructured loans	5	0	0
Decrease in held-to-maturity securities due to the consolidation of a VIE	10	0	0
Increase in held-for-investment loans and other, net due to the consolidation of a VIE	224	0	0
Increase in collateralized borrowings, net due to the consolidation of a VIE	214	0	$ 0
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Consolidated Balance Sheet	15,621	3,555
Restricted cash included in other assets on the Consolidated Balance Sheet	$ 953	$ 825