Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Statement of Cash Flows [Abstract]
Net income (loss)	$ (78)	$ 956
Net Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	802	752
Goodwill impairment	50	0
Provision for credit losses	1,190	459
Gain on mortgage and automotive loans, net	(2)	(12)
Other gain on investments, net	(109)	(147)
Originations and purchases of loans held-for-sale	(1,329)	(528)
Proceeds from sales and repayments of loans held-for-sale	1,167	335
Increase (decrease) in deferred income taxes	0	1
Increase (decrease) in interest payable	56	221
Increase (decrease) in other assets	(420)	(21)
Increase (decrease) in other liabilities	(211)	(114)
Increase (decrease) in other assets and liabilities, net	46	(58)
Net cash provided by operating activities	1,162	1,844
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(740)	(210)
Proceeds from sales of equity securities	774	511
Purchases of available-for-sale securities	7,696	7,018
Proceeds from Sale of Debt Securities, Available-for-sale	5,544	2,568
Proceeds from repayments of available-for-sale securities	4,440	1,805
Purchases of held-to-maturity securities	0	(268)
Proceeds from repayments of held-to-maturity securities	177	107
Purchases of finance receivables and loans held-for-investment	(3,495)	(2,386)
Proceeds from sales of finance receivables and loans initially held-for-investment	1	159
Originations and repayments of finance receivables and loans held-for-investment and other, net	13,135	2,769
Purchases of operating lease assets	(1,949)	(1,769)
Disposals of operating lease assets	1,179	1,321
Net change in nonmarketable equity investments	148	113
Payments for (proceeds from) other, net	(213)	(209)
Net cash provided by (used in) investing activities	11,305	(2,507)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	1,842	3,468
Net increase in deposits	10,272	10,133
Proceeds from issuance of long-term debt	2,372	4,590
Repayments of long-term debt	(7,434)	(11,372)
Repurchase of common stock	(104)	(440)
Dividends paid	(144)	(139)
Net cash provided by (used in) financing activities	3,120	(696)
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	(3)	3
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net increase (decrease) in cash and cash equivalents and restricted cash	15,584	(1,356)
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	19,964	4,270
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	1,722	1,884
Cash paid for income taxes	7	24
Loans held-for-sale transferred to finance receivables and loans held-for-investment	70	125
Finance receivables and loans transferred to loans held-for-sale, noncash	0	20
In-kind distribution from equity method investee	60	0
Equity consideration received in exchange for restructured loans	5	0
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet	19,131	3,563
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	$ 833	$ 707