Off-Balance Sheet Lending-Related Financial Instruments, Guarantees and Other Commitments - Loan Sales- and Securitization-Related Indemnifications (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Summary of changes in mortgage repurchase liability
Repurchase liability at beginning of period	$ 275	$ 681
Net realized gains/(losses)	10	11
Provision for repurchase losses	(33)	(128)
Repurchase liability at end of period	252	564
Loans sold with recourse
Loans sold with recourse
Indemnification agreements loan sale and securitization loans sold with recourse contractual amount	5,637		6,063
Indemnification agreements, loan sale and securitization, loans sold with recourse: carrying value	99		102
Warranty Reserves | Mortgage repurchase liability
Summary of changes in mortgage repurchase liability
Repurchase liability at beginning of period			275
Repurchase liability at end of period	252		275
Repurchase Make-Whole Settlements | Warranty Reserves | Mortgage repurchase liability
Summary of changes in mortgage repurchase liability
Net realized gains/(losses)	(2)	(2)
Reserves for New Mortgage Loans Sold During the Period | Warranty Reserves | Mortgage repurchase liability
Summary of changes in mortgage repurchase liability
Valuation allowances and reserves provision	$ 1	$ 1