Condensed Consolidated Statement of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 374	$ 250
Depreciation and amortization	369	434
Provision for loan losses	282	261
Gain (Loss) on Sales of Loans, Net	(10)	(1)
Gain (Loss) on Investments	(108)	12
Originations and purchases of loans held-for-sale	(134)	(248)
Proceeds from sales and repayments of loans held-for-sale	111	230
Increase (decrease) in deferred income taxes	100	83
Increase (decrease) in interest payable	173	120
Increase (decrease) in other operating assets	(40)	29
Increase (decrease) in other operating liabilities	37	(106)
Increase (decrease) in other operating assets and liabilities, net	(73)	33
Net cash provided by (used in) operating activities	1,081	1,097
Net Cash (Used in) Provided by Investing Activities [Abstract]
Purchases of equity securities	(48)	(374)
Proceeds from sales of equity securities	383	220
Purchases of available-for-sale securities	(3,401)	(2,360)
Proceeds from sale of available-for-sale securities	656	328
Proceeds from repayments of available-for-sale securities	694	795
Purchases of held-to-maturity securities	(131)	(155)
Proceeds from repayments of held-to-maturity securities	44	35
Purchases of finance receivables and loans held-for-investment	(1,452)	(1,497)
Proceeds from sales of finance receivables and loans initially held-for-investment	157	0
Originations and repayments of finance receivables and loans held-for-investment and other, net	1,149	(1,300)
Purchases of operating lease assets	(792)	(969)
Disposals of operating lease assets	624	976
Net change in nonmarketable equity investments	171	(19)
Payments for (proceeds from) other, net	(95)	(82)
Net cash provided by investing activities	(2,041)	(4,402)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in short-term borrowings	(3,872)	(1,848)
Net increase in deposits	7,114	4,173
Proceeds from issuance of long-term debt	1,766	6,665
Repayments of long-term debt	(4,490)	(5,771)
Repurchase of common stock	(211)	(185)
Dividends paid	(70)	(58)
Net cash provided by (used in) financing activities	237	2,976
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	(722)	(331)
Cash and cash equivalents and restricted cash	4,904	4,938
Cash and cash equivalents as disclosed on the Condensed Consolidated Balance Sheet	3,957	3,721
Restricted cash included in other assets on the Condensed Consolidated Balance Sheet	947	1,217
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	862	667
Cash paid for income taxes	12	5
Loans held-for-sale transferred to finance receivables and loans held-for-investment	63	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	$ 3	$ 11