Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Net income	$ (319)	$ 374
Net Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	386	369
Provision for credit losses	903	282
Loss (gain) on mortgage and automotive loans, net	12	(10)
Other loss (gain) on investments, net	79	(108)
Originations and purchases of loans held-for-sale	(366)	(134)
Proceeds from sales and repayments of loans held-for-sale	300	111
Increase (decrease) in deferred income taxes	(87)	100
Increase (decrease) in interest payable	69	173
Increase (decrease) in other assets	44	(40)
Increase (decrease) in other liabilities	(290)	37
Increase (decrease) in other assets and liabilities, net	83	(73)
Net cash provided by operating activities	814	1,081
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(625)	(48)
Proceeds from sales of equity securities	117	383
Purchases of available-for-sale securities	4,565	3,401
Proceeds from Sale of Debt Securities, Available-for-sale	3,817	656
Proceeds from repayments of available-for-sale securities	1,623	694
Purchases of held-to-maturity securities	0	(131)
Proceeds from repayments of held-to-maturity securities	70	44
Purchases of finance receivables and loans held-for-investment	(925)	(1,452)
Proceeds from sales of finance receivables and loans initially held-for-investment	1	157
Originations and repayments of finance receivables and loans held-for-investment and other, net	900	1,149
Purchases of operating lease assets	(1,138)	(792)
Disposals of operating lease assets	568	624
Net change in nonmarketable equity investments	(92)	171
Payments for (proceeds from) other, net	(76)	(95)
Net cash used in investing activities	(325)	(2,041)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	(3,963)	3,872
Net increase in deposits	1,565	7,114
Proceeds from issuance of long-term debt	788	1,766
Repayments of long-term debt	(3,939)	(4,490)
Repurchase of common stock	(104)	(211)
Dividends paid	(72)	(70)
Net cash provided by financing activities	2,201	237
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	(4)	1
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net increase (decrease) in cash and cash equivalents and restricted cash	2,686	(722)
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	4,380	5,626
Cash and cash equivalents and restricted cash	7,066	4,904
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	869	862
Cash paid for income taxes	2	12
Loans held-for-sale transferred to finance receivables and loans held-for-investment	11	63
Finance receivables and loans transferred to loans held-for-sale, noncash	0	20
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet	6,161	3,957
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	$ 905	$ 947