Long-Term Debt (Committed Funding Facilities) (Details) (USD $) In Billions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Committed Funding Facilities [Member]
Debt Instrument [Line Items]
Outstanding	$ 22.7	$ 22.7
Unused capacity	20.5	20.4
Total capacity	43.2	43.1
Committed Funding Facilities [Member] | Bank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	3.8	5.8
Unused capacity	4.7	3.7
Total capacity	8.5	9.5
Line of Credit Facility, Current Borrowing Capacity	4.1
Committed Funding Facilities [Member] | Nonbank Funding [Member]
Debt Instrument [Line Items]
Outstanding	18.8	15.3
Unused capacity	11.8	14.2
Total capacity	30.6	29.5
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | North American Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	8.5	4.2
Unused capacity	8.9	10.2
Total capacity	17.4	14.4
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | International Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	10.2	10.1
Unused capacity	2.8	3.0
Total capacity	13.0	13.1
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | Mortgage Operations [Member]
Debt Instrument [Line Items]
Outstanding	0	0.7
Unused capacity	0	0.5
Total capacity	0	1.2
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Unsecured Debt [Member] | North American Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	0	0
Unused capacity	0	0.5
Total capacity	0	0.5
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Unsecured Debt [Member] | International Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	0.1	0.3
Unused capacity	0.1	0
Total capacity	0.2	0.3
Committed Funding Facilities [Member] | Shared Capacity [Member] | North American Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	0	1.5
Unused capacity	4.0	2.5
Total capacity	4.0	4.0
Committed Funding Facilities [Member] | Shared Capacity [Member] | International Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	0.1	0.1
Unused capacity	0	0
Total capacity	0.1	0.1
Committed Funding Facilities [Member] | Revolving secured funding facilities [Member]
Debt Instrument [Line Items]
Total capacity	33.6
Committed Funding Facilities [Member] | Revolving secured funding facilities 1 year or greater [Member]
Debt Instrument [Line Items]
Total capacity	13.3
Committed funding reliant upon origination of future automotive receivables [Member]
Debt Instrument [Line Items]
Unused capacity	$ 3.1	$ 4.9