Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Net income	$ 956	$ 599
Net Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and amortization	752	865
Provision for loan losses	459	419
Gain on mortgage and automotive loans, net	(12)	(2)
Other gain on investments, net	(147)	(15)
Originations and purchases of loans held-for-sale	(528)	(730)
Proceeds from Sale and Collection of Loans Held-for-sale	335	512
Increase (decrease) in deferred income taxes	1	192
Increase (decrease) in interest payable	221	193
Increase (decrease) in other operating assets	(21)	(25)
Increase (decrease) in other operating liabilities	(114)	(24)
Increase (decrease) in other operating assets and liabilities, net	(58)	25
Net cash provided by operating activities	1,844	2,009
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(210)	(500)
Proceeds from sales of equity securities	511	535
Purchases of available-for-sale securities	7,018	4,094
Proceeds from sales of available-for-sale securities	2,568	390
Proceeds from repayments of available-for-sale securities	1,805	1,621
Purchases of held-to-maturity securities	(268)	(316)
Proceeds from repayments of held-to-maturity securities	107	72
Purchases of finance receivables and loans held-for-investment	(2,386)	(2,611)
Proceeds from sales of finance receivables and loans initially held-for-investment	159	0
Originations and repayments of finance receivables and loans held-for-investment and other, net	2,769	(638)
Purchases of operating lease assets	(1,769)	(2,107)
Disposals of operating lease assets	1,321	1,763
Net change in nonmarketable equity investments	113	(46)
Payments for (proceeds from) other, net	(209)	(186)
Net cash used in investing activities	(2,507)	(6,117)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	(3,468)	(4,305)
Net increase in deposits	10,133	5,441
Proceeds from issuance of long-term debt	4,590	12,940
Repayments of long-term debt	(11,372)	(9,800)
Repurchase of common stock	(440)	(380)
Dividends paid	(139)	(115)
Net cash (used in) provided by financing activities	(696)	3,781
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 decrease in cash and cash equivalents and restricted cash	(1,356)	(330)
Cash and cash equivalents and restricted cash	5,626	5,269
Cash and cash equivalents and restricted cash	4,270	4,939
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	1,884	1,455
Cash paid for income taxes	24	17
Loans held-for-sale transferred to finance receivables and loans held-for-investment	125	0
Finance receivables and loans transferred to loans held-for-sale, noncash	20	0
Proceeds from repayments of mortgage loans held-for-investment originally designated as held-for-sale	7	12
Restricted Cash [Abstract]
Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet	3,563	3,924
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	$ 707	$ 1,015