Long-Term Debt (Committed Funding Facilities) (Details) (USD $) In Billions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Committed Funding Facilities [Member]
Debt Instrument [Line Items]
Outstanding	$ 21.4	$ 22.7
Unused capacity	20.9	20.4
Total capacity	42.3	43.1
Committed Funding Facilities [Member] | Bank Funding Member | Secured Debt [Member]
Debt Instrument [Line Items]
Outstanding	3.9	5.8
Unused capacity	5.6	3.7
Total capacity	9.5	9.5
Committed Funding Facilities [Member] | Nonbank Funding [Member]
Debt Instrument [Line Items]
Outstanding	17.4	15.3
Unused capacity	11.5	14.2
Total capacity	28.9	29.5
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | North American Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	7.4	4.2
Unused capacity	9.3	10.2
Total capacity	16.7	14.4
Committed Funding Facilities [Member] | Nonbank Funding [Member] | Secured Debt [Member] | International Automotive Finance Operations [Member]
Debt Instrument [Line Items]
Outstanding	9.9	10.1
Unused capacity	2.2	3.0
Total capacity	12.1	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	0
Total capacity	0	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	3.8	2.5
Total capacity	3.8	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	33.2
Committed Funding Facilities [Member] | Revolving secured funding facilities 1 year or greater [Member]
Debt Instrument [Line Items]
Total capacity	17.5
Committed funding reliant upon origination of future automotive receivables [Member]
Debt Instrument [Line Items]
Unused capacity	$ 3.6	$ 4.9