Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Cash Flows [Abstract]
Net income (loss)	$ 796	$ (319)
Net Cash Provided by Operating Activities [Abstract]
Depreciation and amortization	373	386
Provision for credit losses	(13)	903
(Gain) loss on mortgage and automotive loans, net	(36)	12
Other (gain) loss on investments, net	(123)	79
Change in Gain (Loss) On Extinguishment Of Debt	1	0
Originations and purchases of loans held-for-sale	(1,175)	(366)
Proceeds from sales and repayments of loans held-for-sale	1,137	300
Increase (decrease) in deferred income taxes	(19)	(87)
Increase (decrease) in interest payable	41	69
Increase (decrease) in other assets	78	44
Increase (decrease) in other liabilities	105	(290)
Increase (decrease) in other assets and liabilities, net	5	83
Net Cash Provided by Operating Activities, Total	1,170	814
Net Cash Procided by (Used in) Investing Activities [Abstract]
Purchases of equity securities	(472)	(625)
Proceeds from sales of equity securities	589	117
Purchases of available-for-sale securities	10,116	4,565
Proceeds from Sale of Debt Securities, Available-for-sale	2,327	3,817
Proceeds from repayments of available-for-sale securities	3,612	1,623
Purchases of held-to-maturity securities	(63)	0
Proceeds from repayments of held-to-maturity securities	118	70
Purchases of finance receivables and loans held-for-investment	(930)	(925)
Proceeds from sales of finance receivables and loans initially held-for-investment	164	1
Originations and repayments of loans held-for-investment and other	5,783	900
Purchases of operating lease assets	(1,269)	(1,138)
Disposals of operating lease assets	780	568
Net change in nonmarketable equity investments	29	(92)
Payments for (proceeds from) other, net	(100)	(76)
Net Cash Provided by (Used in) Investing Activities, Total	452	(325)
Net Cash (Used in) Provided by Financing Activities [Abstract]
Net change in short-term borrowings	2,136	(3,963)
Net increase in deposits	2,545	1,565
Proceeds from issuance of long-term debt	56	788
Repayments of long-term debt	(1,340)	(3,939)
Repurchase of common stock	(219)	(104)
Dividends paid	(73)	(72)
Net Cash (Used in) Provided by Financing Activities, Total	(1,167)	2,201
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations	2	(4)
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	457	2,686
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	16,574	4,380
Cash and cash equivalents and restricted cash	17,031	7,066
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	492	869
Cash paid for income taxes	4	2
Loans held-for-sale transferred to finance receivables and loans held-for-investment	4	11
Additions of property and equipment	46	0
Finance receivables and loans transferred to loans held-for-sale, noncash	329	0
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Consolidated Balance Sheet	15,778	6,161
Restricted cash included in other assets on the Consolidated Balance Sheet	$ 1,253	$ 905