Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Net income (loss)	$ 398	$ 1,337
Net Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	1,159	1,136
Goodwill impairment	50	0
Provision for credit losses	1,337	722
Gain on mortgage and automotive loans, net	(35)	(22)
Other gain on investments, net	(173)	(174)
Change in Gain (Loss) On Extinguishment Of Debt	50	2
Originations and purchases of loans held-for-sale	(2,241)	(952)
Proceeds from sales and repayments of loans held-for-sale	2,107	788
Increase (decrease) in deferred income taxes	122	86
Increase (decrease) in interest payable	107	371
Increase (decrease) in other assets	(196)	(25)
Increase (decrease) in other liabilities	(29)	(98)
Increase (decrease) in other assets and liabilities, net	(52)	(38)
Net cash provided by operating activities	2,604	3,133
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(816)	(301)
Proceeds from sales of equity securities	936	615
Purchases of available-for-sale securities	12,013	11,214
Proceeds from Sale of Debt Securities, Available-for-sale	6,350	5,699
Proceeds from repayments of available-for-sale securities	7,846	3,246
Purchases of held-to-maturity securities	0	(514)
Proceeds from repayments of held-to-maturity securities	306	195
Purchases of finance receivables and loans held-for-investment	(5,188)	(3,322)
Proceeds from sales of finance receivables and loans initially held-for-investment	122	427
Originations and repayments of finance receivables and loans held-for-investment and other, net	14,745	3,069
Purchases of operating lease assets	(3,226)	(2,937)
Disposals of operating lease assets	1,946	2,016
Net change in nonmarketable equity investments	305	179
Payments for (proceeds from) other, net	(308)	(306)
Net cash provided by (used in) investing activities	11,005	(3,148)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	2,499	4,652
Net increase in deposits	14,168	13,032
Proceeds from issuance of long-term debt	3,174	5,438
Repayments of long-term debt	(11,887)	(14,114)
Repurchase of common stock	(105)	(740)
Dividends paid	(217)	(206)
Net cash provided by (used in) financing activities	2,634	(1,242)
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	(1)	2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net increase (decrease) in cash and cash equivalents and restricted cash	16,242	(1,255)
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	20,622	4,371
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	2,414	2,781
Cash paid for income taxes	8	31
Loans held-for-sale transferred to finance receivables and loans held-for-investment	74	125
Finance receivables and loans transferred to loans held-for-sale, noncash	128	964
In-kind distribution from equity method investee	126	0
Equity consideration received in exchange for restructured loans	5	0
Decrease in held-to-maturity securities due to the consolidation of a VIE	5	0
Increase in held-for-investment loans and other, net due to the consolidation of a VIE	114	0
Increase in collateralized borrowings, net due to the consolidation of a VIE	109	0
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet	19,939	3,617
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	$ 683	$ 754