Guarantee Arrangements and Pledged Assets and Collateral - Offsetting of Resale and Repurchase Agreements and Securities Borrowing and Lending Agreements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Securities purchased under agreements to resell, Gross Amounts Recognized	$ 8,608		$ 7,165
Securities purchased under agreements to resell, Gross Amounts Offset in the Balance Sheet	1,643	[1]	5,752	[1]
Securities Purchased under Agreements to Resell	6,965		1,413
Securities purchased under agreements to resell, Gross Amounts Not Offset in the Balance Sheet, Financial Instruments	6,965	[2]	1,413	[2]
Securities purchased under agreements to resell, Gross Amounts Not Offset in the Balance Sheet, Cash Collateral Receive / Pledged	0		0
Securities purchased under agreements to resell, Net amount	0	[3]	0	[3]
Securities sold under repurchase agreements, Gross Amounts Recognized	13,860		13,459
Securities sold under repurchase agreements, Gross Amounts Offset in the Balance Sheet	1,643	[1]	5,752	[1]
Securities sold under repurchase agreements, Net Amounts Presented in the Balance Sheet	12,217		7,707
Securities sold under repurchase agreements, Gross Amounts Not Offset in the Balance sheet, Financial Instruments	12,217	[2]	7,707	[2]
Securities sold under repurchase agreements, Gross Amounts Not Offset in the Balance Sheet, Cash Collateral Received / Pledged	0		0
Securities sold under repurchase agreements, Net amount	$ 0	[3]	$ 0	[3]

[1] Represents recognized amount of resale and repurchase agreements with counterparties subject to legally enforceable netting agreements that meet the applicable netting criteria as permitted by generally accepted accounting principles.

[2] Represents securities received or pledged to cover financing transaction exposures.

[3] Represents the amount of our exposure that is not collateralized / covered by pledged collateral.