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, 2015	Mar. 31, 2014	Dec. 31, 2014
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	$ 105,578		$ 105,681
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	498		655
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	151	136
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	101,416		101,951
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	473		617
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	150	133
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	58,947		58,085
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	332		457
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	132	121
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	7,695		7,926
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	133		151
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	19	12
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	32,753		34,022
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	8		9
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	(1)	0
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	2,021		1,918
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	0	0
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	2,500		2,801
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	4		5
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	2,500		2,801
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	4		5
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	0
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	1,662		929
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	21		33
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 0	$ 3