Long-Term Debt (Committed Funding Facilities) (Details) (USD $) In Billions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Committed Funding Facilities [Member]
Debt Instrument [Line Items]
Outstanding	$ 11.6	$ 27.5
Unused capacity	16.0	15.5
Total capacity	27.6	43.0
Committed Funding Facilities [Member] | Bank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	1.7	3.8
Unused capacity	1.8	4.7
Total capacity	3.5	8.5
Committed Funding Facilities [Member] | Nonbank Funding [Member]
Debt Instrument [Line Items]
Outstanding	9.9	22.6
Unused capacity	14.2	7.8
Total capacity	24.1	30.4
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	9.9	22.5
Unused capacity	14.2	7.8
Total capacity	24.1	30.3
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | International Businesses [Member]
Debt Instrument [Line Items]
Outstanding	2.2	9.6
Total capacity	2.8	12.0
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Outstanding	0	0.1
Unused capacity	0	0
Total capacity	0	0.1
Committed Funding Facilities [Member] | Shared Capacity [Member]
Debt Instrument [Line Items]
Outstanding	0	1.1
Unused capacity	0	3.0
Total capacity	0	4.1
Committed Funding Facilities [Member] | Shared Capacity [Member] | International Businesses [Member]
Debt Instrument [Line Items]
Outstanding		0.1
Total capacity		0.1
Committed Funding Facilities [Member] | Revolving secured funding facilities [Member]
Debt Instrument [Line Items]
Total capacity	24.2
Committed Funding Facilities [Member] | Revolving secured funding facilities 1 year or greater [Member]
Debt Instrument [Line Items]
Total capacity	14.5
Committed funding reliant upon origination of future automotive receivables [Member]
Debt Instrument [Line Items]
Unused capacity	$ 0.8	$ 2.2