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	Jun. 30, 2013		Dec. 31, 2012
Offsetting [Abstract]
Securities purchased under agreements to resell, Gross Amounts Recognized	$ 9,210		$ 5,736
Securities sold under repurchase agreements, Gross Amounts Offset in the Balance Sheet	7,811	[1]	2,587	[1]
Securities purchased under agreements to resell, Net Amounts Presented in the Balance Sheet	1,399		3,149
Securities purchased under agreements to resell, Gross Amounts Not Offset in the Balance SHeet, Financial Instruments	1,393	[2]	3,146	[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	6	[3]	3	[3]
Securities sold under repurchase agreements, Gross Amounts Recognized	20,256		9,404
Securities sold under repurchase agreements, Gross Amounts Offset in the Balance Sheet	7,811	[1]	2,587	[1]
Securities sold under repurchase agreements, Net Amounts Presented in the Balance Sheet	12,445		6,817
Securities sold under repurchase agreements, Gross Amounts Not Offset in the Balance sheet, Financial Instruments	12,445	[2]	6,817	[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.