Debt - Short Term and Long Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Short Term and Long Term Debt [Line Items]
Secured debt	$ 28,284	$ 25,214
Unsecured debt	19,975	12,217
Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	7,855	7,028
Unsecured debt	2,344	2,974
Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	16,394	8,450
Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	1,237	793
North America Segment [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	20,101	15,454
Unsecured debt	15,111	7,846
North America Segment [Member] | Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	3,353	1,701
Unsecured debt	0	0
North America Segment [Member] | Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	15,111	7,846
North America Segment [Member] | Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	0	0
International Segment [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	8,183	9,760
Unsecured debt	4,864	4,371
International Segment [Member] | Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	4,502	5,327
Unsecured debt	2,344	2,974
International Segment [Member] | Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	1,283	604
International Segment [Member] | Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	1,237	793
Consumer Portfolio Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	18,323	16,121
Consumer Portfolio Segment [Member] | North America Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	15,498	13,253
Consumer Portfolio Segment [Member] | International Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	2,825	2,868
Commercial Finance Receivables [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	2,106	2,065
Commercial Finance Receivables [Member] | North America Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	1,250	500
Commercial Finance Receivables [Member] | International Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	$ 856	$ 1,565