Securitization and Variable Interest Entities (Schedule of Net Credit Losses for Securitized and Other Financial Assets Managed Together) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 98	$ 1,211	$ 1,702	$ 4,246
On-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	96	119	229	411
Off-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	910	1,235	3,209
Whole-Loan Transactions [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	182	238	626
Consumer Loans Auto Financing Receivable [Member] | On-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	96	71	240	243
Consumer Loans Auto Financing Receivable [Member] | Off-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	0	1	0
Residential Mortgage [Member] | On-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	47	20	130
Private Placement [Member] | Off-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	0	910	1,234	3,209
Commercial Automobile [Member] | On-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	0	1	11
Commercial Finance Receivables And Loans, Mortgage [Member] | On-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	0	1	(1)	26
Commercial Other [Member] | On-Balance Sheet Loans [Member]
Net Credit Losses for Securitized and Other Financial Assets Managed Together [Line Items]
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ (4)	$ 0	$ (31)	$ 1