Parent and Guarantor Condensed Consolidating Financial Statements (Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by (used in) operating activities			$ 1,844	$ 2,009
Purchases of equity securities			(210)	(500)
Proceeds from sales of equity securities			511	535
Payments to Acquire Debt Securities, Available-for-sale			(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)
Net change in intercompany loans	$ 2	$ 1	12	2
Purchases of operating lease assets			(1,769)	(2,107)
Disposals of operating lease assets			1,321	1,763
Capital contributions to subsidiaries			0	0
Returns of contributed capital			0	0
Net change in nonmarketable equity investments			113	(46)
Payments for (proceeds from) other, net			(209)	(186)
Net cash provided by investing activities			(2,507)	(6,117)
Net change in short-term borrowings			(3,468)	(4,305)
Net (decrease) 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)
Capital contributions from parent			0	0
Net cash provided by (used in) financing activities			(696)	3,781
Effect of exchange-rate changes on cash and cash equivalents and restricted cash			3	(3)
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	4,270	4,939
Cash and cash equivalents	3,563	3,924	3,563	3,924	$ 4,537
Restricted Cash	707	1,015	707	1,015
Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities			0	0
Net change in intercompany loans			0	0
Net Change in Debt, Intercompany			0	0
Dividends paid and returns of contributed capital, intercompany			0	0
Consolidating adjustments
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by (used in) operating activities			(1,938)	(3,302)
Purchases of equity securities			0	0
Proceeds from sales of equity securities			0	0
Payments to Acquire Debt Securities, Available-for-sale			0	0
Proceeds from sales of available-for-sale securities			0	0
Proceeds from repayments of available-for-sale securities			0	0
Purchases of held-to-maturity securities			0	0
Proceeds from repayments of held-to-maturity securities			0	0
Purchases of finance receivables and loans held-for-investment			464	820
Proceeds from sales of finance receivables and loans initially held-for-investment			(464)	(820)
Originations and repayments of finance receivables and loans held-for-investment and other, net			3	0
Net change in intercompany loans	0	0	0	(28)
Purchases of operating lease assets			0	0
Disposals of operating lease assets			0	0
Capital contributions to subsidiaries			1	63
Returns of contributed capital			(26)	(194)
Net change in nonmarketable equity investments			0	0
Payments for (proceeds from) other, net			(1)	0
Net cash provided by investing activities			(536)	(226)
Net change in short-term borrowings			0	0
Net (decrease) increase in deposits			7	123
Proceeds from issuance of long-term debt			0	0
Repayments of long-term debt			0	0
Repurchase of common stock			0	0
Dividends paid			0	0
Capital contributions from parent			(1)	(63)
Net cash provided by (used in) financing activities			2,257	3,776
Effect of exchange-rate changes on cash and cash equivalents and restricted cash			0	0
Net decrease in cash and cash equivalents and restricted cash			(217)	248
Cash and cash equivalents and restricted cash			(1,770)	(1,833)
Cash and cash equivalents and restricted cash	(1,987)	(1,585)	(1,987)	(1,585)
Cash and cash equivalents	(1,987)	(1,585)	(1,987)	(1,585)	(1,770)
Restricted Cash	0	0	0	0
Consolidating adjustments | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities			(6)	(17)
Net change in intercompany loans			(507)	(78)
Net Change in Debt, Intercompany			290	221
Dividends paid and returns of contributed capital, intercompany			1,961	3,495
Parent
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by (used in) operating activities			693	958
Purchases of equity securities			0	0
Proceeds from sales of equity securities			0	0
Payments to Acquire Debt Securities, Available-for-sale			0	0
Proceeds from sales of available-for-sale securities			0	0
Proceeds from repayments of available-for-sale securities			0	0
Purchases of held-to-maturity securities			0	0
Proceeds from repayments of held-to-maturity securities			0	0
Purchases of finance receivables and loans held-for-investment			0	0
Proceeds from sales of finance receivables and loans initially held-for-investment			476	820
Originations and repayments of finance receivables and loans held-for-investment and other, net			(407)	1,331
Net change in intercompany loans	(1)	0	3	28
Purchases of operating lease assets			0	0
Disposals of operating lease assets			2	6
Capital contributions to subsidiaries			(1)	(57)
Returns of contributed capital			26	194
Net change in nonmarketable equity investments			(11)	0
Payments for (proceeds from) other, net			0	(3)
Net cash provided by investing activities			301	2,374
Net change in short-term borrowings			(15)	(505)
Net (decrease) increase in deposits			0	(6)
Proceeds from issuance of long-term debt			756	32
Repayments of long-term debt			(1,116)	(2,412)
Repurchase of common stock			(440)	(380)
Dividends paid			(139)	(115)
Capital contributions from parent			0	0
Net cash provided by (used in) financing activities			(1,028)	(3,524)
Effect of exchange-rate changes on cash and cash equivalents and restricted cash			0	0
Net decrease in cash and cash equivalents and restricted cash			(34)	(192)
Cash and cash equivalents and restricted cash			1,398	1,395
Cash and cash equivalents and restricted cash	1,364	1,203	1,364	1,203
Cash and cash equivalents	1,292	1,071	1,292	1,071	1,309
Restricted Cash	72	132	72	132
Parent | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities			0	0
Net change in intercompany loans			216	83
Net Change in Debt, Intercompany			(74)	(138)
Dividends paid and returns of contributed capital, intercompany			0	0
Guarantors
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by (used in) operating activities			900	1,500
Purchases of equity securities			0	0
Proceeds from sales of equity securities			0	0
Payments to Acquire Debt Securities, Available-for-sale			0	0
Proceeds from sales of available-for-sale securities			0	0
Proceeds from repayments of available-for-sale securities			0	0
Purchases of held-to-maturity securities			0	0
Proceeds from repayments of held-to-maturity securities			0	0
Purchases of finance receivables and loans held-for-investment			0	0
Proceeds from sales of finance receivables and loans initially held-for-investment			0	0
Originations and repayments of finance receivables and loans held-for-investment and other, net			0	0
Net change in intercompany loans	0	0	0	0
Purchases of operating lease assets			0	0
Disposals of operating lease assets			0	0
Capital contributions to subsidiaries			0	(6)
Returns of contributed capital			0	0
Net change in nonmarketable equity investments			0	0
Payments for (proceeds from) other, net			0	0
Net cash provided by investing activities			0	(6)
Net change in short-term borrowings			0	0
Net (decrease) increase in deposits			0	0
Proceeds from issuance of long-term debt			0	0
Repayments of long-term debt			0	0
Repurchase of common stock			0	0
Dividends paid			0	0
Capital contributions from parent			0	6
Net cash provided by (used in) financing activities			(900)	(1,494)
Effect of exchange-rate changes on cash and cash equivalents and restricted cash			0	0
Net decrease in cash and cash equivalents and restricted cash			0	0
Cash and cash equivalents and restricted cash			0	0
Cash and cash equivalents and restricted cash	0	0	0	0
Cash and cash equivalents	0	0	0	0	0
Restricted Cash	0	0	0	0
Guarantors | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities			0	0
Net change in intercompany loans			0	0
Net Change in Debt, Intercompany			0	0
Dividends paid and returns of contributed capital, intercompany			(900)	(1,500)
Nonguarantors
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net cash provided by (used in) operating activities			2,189	2,853
Purchases of equity securities			(210)	(500)
Proceeds from sales of equity securities			511	535
Payments to Acquire Debt Securities, Available-for-sale			(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			(2,850)	(3,431)
Proceeds from sales of finance receivables and loans initially held-for-investment			147	0
Originations and repayments of finance receivables and loans held-for-investment and other, net			3,173	(1,969)
Net change in intercompany loans	3	1	9	2
Purchases of operating lease assets			(1,769)	(2,107)
Disposals of operating lease assets			1,319	1,757
Capital contributions to subsidiaries			0	0
Returns of contributed capital			0	0
Net change in nonmarketable equity investments			124	(46)
Payments for (proceeds from) other, net			(208)	(183)
Net cash provided by investing activities			(2,272)	(8,259)
Net change in short-term borrowings			(3,453)	(3,800)
Net (decrease) increase in deposits			10,126	5,324
Proceeds from issuance of long-term debt			3,834	12,908
Repayments of long-term debt			(10,256)	(7,388)
Repurchase of common stock			0	0
Dividends paid			0	0
Capital contributions from parent			1	57
Net cash provided by (used in) financing activities			(1,025)	5,023
Effect of exchange-rate changes on cash and cash equivalents and restricted cash			3	(3)
Net decrease in cash and cash equivalents and restricted cash			(1,105)	(386)
Cash and cash equivalents and restricted cash			5,998	5,707
Cash and cash equivalents and restricted cash	4,893	5,321	4,893	5,321
Cash and cash equivalents	4,258	4,438	4,258	4,438	$ 4,998
Restricted Cash	$ 635	$ 883	635	883
Nonguarantors | Affiliated entity
Parent and Guarantor Consolidating Statement of Cash Flows [Line Items]
Net change in intercompany investment securities			6	17
Net change in intercompany loans			291	(5)
Net Change in Debt, Intercompany			(216)	(83)
Dividends paid and returns of contributed capital, intercompany			$ (1,061)	$ (1,995)