Securities Financing Transactions (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Collateral Received that Can be Resold or Repledged [Abstract]
Fair value of securities received as collateral that can be resold or repledged	$ 512,000,000,000	$ 500,000,000,000
Fair value of securities received as collateral that have been resold or repledged	404,000,000,000	405,000,000,000
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	32,382,000,000	70,059,000,000
Equities and convertible debentures
Collateral Received that Can be Resold or Repledged [Abstract]
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	13,234,000,000	11,732,000,000
Corporate debt and preferred stock
Collateral Received that Can be Resold or Repledged [Abstract]
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	5,358,000,000	8,368,000,000
U.S. Government and agencies
Collateral Received that Can be Resold or Repledged [Abstract]
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	9,531,000,000	41,236,000,000
Non-U.S. governments and agencies
Collateral Received that Can be Resold or Repledged [Abstract]
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	2,164,000,000	1,707,000,000
Mortgages, mortgage-backed, and asset-backed securities
Collateral Received that Can be Resold or Repledged [Abstract]
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	1,813,000,000	4,547,000,000
Municipals and money markets
Collateral Received that Can be Resold or Repledged [Abstract]
Financial instruments owned and pledged as collateral, amount not eligible to be repledged by counterparty	$ 282,000,000	$ 2,469,000,000