Long-Term Debt (Committed Funding Facilities) (Details) (USD $) In Billions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Committed Funding Facilities [Member]
Debt Instrument [Line Items]
Outstanding	$ 10.7	$ 27.5
Unused capacity	17.6	15.5
Total capacity	28.3	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	9.0	22.6
Unused capacity	11.7	7.8
Total capacity	20.7	30.4
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	9.0	22.5
Unused capacity	11.7	7.8
Total capacity	20.7	30.3
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | International Businesses [Member]
Debt Instrument [Line Items]
Outstanding	2.0	9.6
Total capacity	2.5	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	4.1	3.0
Total capacity	4.1	4.1
Line of Credit Facility, Current Borrowing Capacity	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	23.7
Committed Funding Facilities [Member] | Revolving secured funding facilities 1 year or greater [Member]
Debt Instrument [Line Items]
Total capacity	13.5
Committed funding reliant upon origination of future automotive receivables [Member]
Debt Instrument [Line Items]
Unused capacity	$ 1.5	$ 2.2