Fair Value (Fair Value Option for Certain Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Option, Quantitative Disclosures [Line Items]
Carrying value at estimated fair value	$ 57,139	$ 57,706
Carrying value at estimated fair value	16,793	18,653
Consolidated Securitization Entities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Unpaid principal balance	1,068	1,528
Difference between estimated fair value and unpaid principal balance	72	70
Carrying value at estimated fair value	1,140	1,598
Loans in non-accrual status	0	0
Loans more than 90 days past due	0	0
Loans in non-accrual status or more than 90 days past due, or both - difference between aggregate estimated fair value and unpaid principal balance	0	0
Contractual principal balance	985	1,445
Difference between estimated fair value and contractual principal balance	11	10
Carrying value at estimated fair value	996	1,455
Residential Mortgage Loans - FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Unpaid principal balance	537	508
Difference between estimated fair value and unpaid principal balance	(185)	(170)
Carrying value at estimated fair value	352	338
Loans in non-accrual status	134	0
Loans more than 90 days past due	98	81
Loans in non-accrual status or more than 90 days past due, or both - difference between aggregate estimated fair value and unpaid principal balance	$ (114)	$ (82)