Securitizations And Variable Interest Entities (Schedule Of Quantitative Information and Net Credit Losses about Securitized and Other Financial Assets Managed Together) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	$ 102,918		$ 102,918		$ 229,266
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	653		653		2,642
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	109	45	224	135
On-Balance Sheet Loans [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	97,095		97,095		101,631
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	556		556		617
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	103	43	217	125
On-Balance Sheet Loans [Member] | Consumer Loans Auto Financing Receivable [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	56,028		56,028		53,715
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	327		327		351
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	80	70	173	144
On-Balance Sheet Loans [Member] | Residential Mortgage [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	9,326		9,326		12,311
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	201		201		241
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	26	(8)	47	10
On-Balance Sheet Loans [Member] | Commercial Automobile [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	30,193		30,193		32,822
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	28		28		24
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	(1)	(1)	0	(1)
On-Balance Sheet Loans [Member] | Commercial Finance Receivables And Loans, Mortgage [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	0		0		0
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	0		0		0
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	0	0	0	(1)
On-Balance Sheet Loans [Member] | Commercial Other [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	1,548		1,548		2,783
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	0		0		1
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	(2)	(18)	(3)	(27)
Off-Balance Sheet Loans [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	1,314		1,314		120,879
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	3		3		1,896
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	0	2	0
Off-Balance Sheet Loans [Member] | Consumer Loans Auto Financing Receivable [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	1,183		1,183		1,495
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	3		3		4
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	0	2	0
Off-Balance Sheet Loans [Member] | US Government-sponsored Enterprises [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	131		131		119,384
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement					1,892
Whole-Loan Transactions [Member]
Quantitative Information about Securitized and Other Financial Assets Managed Together [Line Items]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	4,509		4,509		6,756
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	94		94		129
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 5	$ 2	$ 5	$ 10