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	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
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	$ 105,681	$ 104,110
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	655	690
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	544	481
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	101,951	100,363
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	617	618
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	537	472
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	58,085	56,417
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	457	412
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	501	402
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	7,926	8,460
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	151	164
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	43	75
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	34,022	33,803
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	9	42
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	2
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	1,918	1,683
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	(8)	(7)
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	2,801	899
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	5	3
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	3
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	2,801	899
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	5	3
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	1	3
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	929	2,848
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	33	69
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 6	$ 6