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
	Mar. 31, 2013	Mar. 31, 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	$ 224,077		$ 229,266
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	2,491		2,642
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	115	91
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	99,841		101,631
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	550		617
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	114	83
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	55,014		53,715
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	285		351
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	93	74
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	10,373		12,311
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	226		241
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	21	18
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	31,875		32,822
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	39		24
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	0
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
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	0		0
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		(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	2,579		2,783
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	0		1
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	(1)	(8)
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	118,678		120,879
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	1,838		1,896
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	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	1,336		1,495
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	3		4
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1
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	117,342		119,384
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	1,835		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	5,558		6,756
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	103		129
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		$ 8