Parent and Guarantor Condensed Consolidating Financial Statements (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	$ 4,050	$ 4,150	$ 4,079
Purchases of equity securities	(498)	(1,076)	(899)
Proceeds from sales of equity securities	814	787	1,049
Purchases of available-for-sale securities	(15,199)	(7,868)	(10,335)
Proceeds from sales of available-for-sale securities	7,079	852	3,584
Proceeds from repayments of available-for-sale securities	5,154	3,215	2,899
Purchases of held-to-maturity securities	(514)	(578)	(1,026)
Proceeds from repayments of held-to-maturity securities	302	147	68
Purchases of finance receivables and loans held-for-investment	(4,439)	(5,693)	(5,452)
Proceeds from sales of finance receivables and loans initially held-for-investment	1,038	91	1,339
Originations and repayments of finance receivables and loans held-for-investment and other, net	4,252	(3,245)	(1,063)
Net change in intercompany loans	28	25	68
Purchases of operating lease assets	(4,023)	(3,709)	(4,052)
Disposals of operating lease assets	2,625	3,089	5,567
Acquisitions, net of acquired cash	(171)	0	0
Capital contributions to subsidiaries	0	0	0
Returns of contributed capital	0	0	0
Net change in nonmarketable equity investments	190	(181)	(187)
Payments for (proceeds from) other, net	(379)	(340)	(219)
Net cash provided by (used in) investing activities	(3,769)	(14,509)	(8,727)
Net change in short-term borrowings	(4,456)	(1,426)	(1,263)
Net (decrease) increase in deposits	14,547	12,867	14,172
Proceeds from issuance of long-term debt	6,915	18,401	17,969
Repayments of long-term debt	(17,224)	(17,940)	(27,908)
Repurchase of common stock	(1,039)	(939)	(753)
Dividends paid	(273)	(242)	(184)
Capital contributions from parent	0	0	0
Net cash provided by (used in) financing activities	(1,530)	10,721	2,033
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	3	(5)	3
Cash and cash equivalents	3,555	4,537
Restricted Cash	825	1,089
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net decrease in cash and cash equivalents and restricted cash	(1,246)	357	(2,612)
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	4,380	5,626	5,269
Cash and cash equivalents and restricted cash	5,626	5,269	7,881
Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities	0	0	0
Net change in intercompany loans	0	0	0
Net Change in Debt, Intercompany	0	0	0
Dividends paid and returns of contributed capital, intercompany	0	0	0
Consolidating adjustments
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	(4,346)	(5,645)	(7,278)
Purchases of equity securities	0	0	0
Proceeds from sales of equity securities	0	0	0
Purchases of available-for-sale securities	0	0	0
Proceeds from sales of available-for-sale securities	0	0	0
Proceeds from repayments of available-for-sale securities	0	0	0
Purchases of held-to-maturity securities	0	0	0
Proceeds from repayments of held-to-maturity securities	0	0	0
Purchases of finance receivables and loans held-for-investment	535	1,539	0
Proceeds from sales of finance receivables and loans initially held-for-investment	(535)	(1,539)	0
Originations and repayments of finance receivables and loans held-for-investment and other, net	8	0	(1,956)
Net change in intercompany loans	0	(54)	0
Purchases of operating lease assets	0	0	0
Disposals of operating lease assets	0	0	0
Acquisitions, net of acquired cash	0
Capital contributions to subsidiaries	2	67	1,217
Returns of contributed capital	(259)	(266)	(1,567)
Net change in nonmarketable equity investments	0	0	0
Payments for (proceeds from) other, net	0	0	(89)
Net cash provided by (used in) investing activities	(1,261)	(231)	(4,978)
Net change in short-term borrowings	0	0	0
Net (decrease) increase in deposits	(802)	(111)	(1,138)
Proceeds from issuance of long-term debt	0	0	1,961
Repayments of long-term debt	0	0	0
Repurchase of common stock	0	0	0
Dividends paid	0	0	0
Capital contributions from parent	(2)	(67)	(1,217)
Net cash provided by (used in) financing activities	4,239	5,939	10,824
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	0	0	0
Cash and cash equivalents	(3,138)	(1,770)
Restricted Cash	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net decrease in cash and cash equivalents and restricted cash	(1,368)	63	(1,432)
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	(3,138)	(1,770)	(1,833)
Cash and cash equivalents and restricted cash	(1,770)	(1,833)	(401)
Consolidating adjustments | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities	(10)	(54)	(298)
Net change in intercompany loans	(1,002)	22	(2,285)
Net Change in Debt, Intercompany	447	208	2,299
Dividends paid and returns of contributed capital, intercompany	4,596	5,909	8,919
Parent
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	1,818	1,659	4,591
Purchases of equity securities	0	0	0
Proceeds from sales of equity securities	0	0	0
Purchases of available-for-sale securities	0	0	0
Proceeds from sales of available-for-sale securities	0	0	0
Proceeds from repayments of available-for-sale securities	0	0	0
Purchases of held-to-maturity securities	0	0	0
Proceeds from repayments of held-to-maturity securities	0	0	0
Purchases of finance receivables and loans held-for-investment	0	(131)	(35)
Proceeds from sales of finance receivables and loans initially held-for-investment	548	1,596	106
Originations and repayments of finance receivables and loans held-for-investment and other, net	(253)	3,489	860
Net change in intercompany loans	4	70	40
Purchases of operating lease assets	0	0	0
Disposals of operating lease assets	3	10	13
Acquisitions, net of acquired cash	0
Capital contributions to subsidiaries	(2)	(61)	(1,212)
Returns of contributed capital	259	266	1,567
Net change in nonmarketable equity investments	(13)	(16)	0
Payments for (proceeds from) other, net	(4)	0	(31)
Net cash provided by (used in) investing activities	1,256	5,133	3,343
Net change in short-term borrowings	104	(694)	(453)
Net (decrease) increase in deposits	0	(11)	(156)
Proceeds from issuance of long-term debt	801	69	354
Repayments of long-term debt	(2,173)	(4,774)	(6,111)
Repurchase of common stock	(1,039)	(939)	(753)
Dividends paid	(273)	(242)	(184)
Capital contributions from parent	0	0	0
Net cash provided by (used in) financing activities	(2,309)	(6,789)	(7,528)
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	0	0	0
Cash and cash equivalents	2,105	1,309
Restricted Cash	58	89
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net decrease in cash and cash equivalents and restricted cash	765	3	406
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	2,163	1,398	1,395
Cash and cash equivalents and restricted cash	1,398	1,395	989
Parent | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities	0	0	7
Net change in intercompany loans	718	(20)	2,068
Net Change in Debt, Intercompany	271	(198)	(225)
Dividends paid and returns of contributed capital, intercompany	0	0	0
Guarantors
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	1,950	2,600	3,300
Purchases of equity securities	0	0	0
Proceeds from sales of equity securities	0	0	0
Purchases of available-for-sale securities	0	0	0
Proceeds from sales of available-for-sale securities	0	0	0
Proceeds from repayments of available-for-sale securities	0	0	0
Purchases of held-to-maturity securities	0	0	0
Proceeds from repayments of held-to-maturity securities	0	0	0
Purchases of finance receivables and loans held-for-investment	0	0	0
Proceeds from sales of finance receivables and loans initially held-for-investment	0	0	0
Originations and repayments of finance receivables and loans held-for-investment and other, net	0	0	0
Net change in intercompany loans	0	0	0
Purchases of operating lease assets	0	0	0
Disposals of operating lease assets	0	0	0
Acquisitions, net of acquired cash	0
Capital contributions to subsidiaries	0	(6)	(5)
Returns of contributed capital	0	0	0
Net change in nonmarketable equity investments	0	0	0
Payments for (proceeds from) other, net	0	0	0
Net cash provided by (used in) investing activities	0	(6)	(5)
Net change in short-term borrowings	0	0	0
Net (decrease) increase in deposits	0	0	0
Proceeds from issuance of long-term debt	0	0	0
Repayments of long-term debt	0	0	0
Repurchase of common stock	0	0	0
Dividends paid	0	0	0
Capital contributions from parent	0	6	5
Net cash provided by (used in) financing activities	(1,950)	(2,594)	(3,295)
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	0	0	0
Cash and cash equivalents	0	0
Restricted Cash	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net decrease in cash and cash equivalents and restricted cash	0	0	0
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	0	0	0
Cash and cash equivalents and restricted cash	0	0	0
Guarantors | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities	0	0	0
Net change in intercompany loans	0	0	0
Net Change in Debt, Intercompany	0	0	0
Dividends paid and returns of contributed capital, intercompany	(1,950)	(2,600)	(3,300)
Nonguarantors
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	4,628	5,536	3,466
Purchases of equity securities	(498)	(1,076)	(899)
Proceeds from sales of equity securities	814	787	1,049
Purchases of available-for-sale securities	(15,199)	(7,868)	(10,335)
Proceeds from sales of available-for-sale securities	7,079	852	3,584
Proceeds from repayments of available-for-sale securities	5,154	3,215	2,899
Purchases of held-to-maturity securities	(514)	(578)	(1,026)
Proceeds from repayments of held-to-maturity securities	302	147	68
Purchases of finance receivables and loans held-for-investment	(4,974)	(7,101)	(5,417)
Proceeds from sales of finance receivables and loans initially held-for-investment	1,025	34	1,233
Originations and repayments of finance receivables and loans held-for-investment and other, net	4,497	(6,734)	33
Net change in intercompany loans	24	9	28
Purchases of operating lease assets	(4,023)	(3,709)	(4,052)
Disposals of operating lease assets	2,622	3,079	5,554
Acquisitions, net of acquired cash	(171)
Capital contributions to subsidiaries	0	0	0
Returns of contributed capital	0	0	0
Net change in nonmarketable equity investments	203	(165)	(187)
Payments for (proceeds from) other, net	(375)	(340)	(99)
Net cash provided by (used in) investing activities	(3,764)	(19,405)	(7,087)
Net change in short-term borrowings	(4,560)	(732)	(810)
Net (decrease) increase in deposits	15,349	12,989	15,466
Proceeds from issuance of long-term debt	6,114	18,332	15,654
Repayments of long-term debt	(15,051)	(13,166)	(21,797)
Repurchase of common stock	0	0	0
Dividends paid	0	0	0
Capital contributions from parent	2	61	1,212
Net cash provided by (used in) financing activities	(1,510)	14,165	2,032
Effect of exchange-rate changes on cash and cash equivalents and restricted cash	3	(5)	3
Cash and cash equivalents	4,588	4,998
Restricted Cash	767	1,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Net decrease in cash and cash equivalents and restricted cash	(643)	291	(1,586)
Cash and cash equivalents and restricted cash [Roll Forward]
Cash and cash equivalents and restricted cash	5,355	5,998	5,707
Cash and cash equivalents and restricted cash	5,998	5,707	7,293
Nonguarantors | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities	10	54	291
Net change in intercompany loans	284	(2)	217
Net Change in Debt, Intercompany	(718)	(10)	(2,074)
Dividends paid and returns of contributed capital, intercompany	$ (2,646)	$ (3,309)	$ (5,619)