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	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
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	$ 117,531		$ 116,486
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	575		721
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	181	$ 151
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	110,915		111,705
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	559		699
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	179	150
On-Balance Sheet Loans [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [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	63,013		64,292
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	462		591
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	173	132
On-Balance Sheet Loans [Member] | Consumer Portfolio Segment [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	10,675		9,773
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	97		108
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	6	19
On-Balance Sheet Loans [Member] | Commercial Portfolio Segment [Member] | Automobile Loan [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	34,325		34,895
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	(1)
On-Balance Sheet Loans [Member] | Commercial Portfolio Segment [Member] | Other Financing Receivables [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	2,902		2,745
Delinquent Amount at End of Period on Loans Managed and 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	3,139		2,529
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	2	1
Off-Balance Sheet Loans [Member] | Consumer Portfolio Segment [Member] | Automobile Loan [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	3,139		2,529
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	2	$ 1
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	3,477		2,252
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	$ 8		$ 13