Debt - Short Term and Long Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Short Term and Long Term Debt [Line Items]
Secured debt	$ 26,617	$ 25,214
Unsecured debt	17,713	12,217
Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	6,211	7,028
Unsecured debt	2,848	2,974
Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	14,143	8,450
Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	722	793
North America Segment [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	17,693	15,454
Unsecured debt	12,862	7,846
North America Segment [Member] | Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	1,008	1,701
Unsecured debt	0	0
North America Segment [Member] | Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	12,862	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	8,924	9,760
Unsecured debt	4,851	4,371
International Segment [Member] | Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	5,203	5,327
Unsecured debt	2,848	2,974
International Segment [Member] | Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	1,281	604
International Segment [Member] | Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	722	793
Consumer Portfolio Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	18,225	16,121
Consumer Portfolio Segment [Member] | North America Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	15,435	13,253
Consumer Portfolio Segment [Member] | International Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	2,790	2,868
Commercial Finance Receivables [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	2,181	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	$ 931	$ 1,565