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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 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	$ 121,305		$ 121,305		$ 116,486
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	700		700		721
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	216	$ 162	552	$ 414
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	115,015		115,015		111,705
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	683		683		699
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	213	161	544	411
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	64,816		64,816		64,292
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	603		603		591
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	219	156	540	384
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	10,857		10,857		9,773
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	80		80		108
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	(6)	6	4	29
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	36,036		36,036		34,895
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	0
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	3,306		3,306		2,745
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	(1)	0	(2)
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	2,734		2,734		2,529
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	11		11		9
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	1	6	3
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	2,734		2,734		2,529
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	11		11		9
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	2	1	6	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	3,556		3,556		2,252
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	6		6		$ 13
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	$ 1	$ 0	$ 2	$ 0