Derivatives Instruments - Collateral (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative
Derivative Liabilities, Net Amount After Liquid Securities and/or Cash Collateral Held at Third-Party Custodians, Liabilities Subject to a Master Netting Agreement	$ 32,530	$ 29,181
Derivatives Assets, Subject to Master Netting Arrangement	51,735	45,982
Derivative, Collateral, Obligation to Return Securities and/or Cash Held by Third-Party Custodians	10,508	11,350
Derivative Assets, Net Exposure After Liquid Securities Collateral, Assets Subject to a Master Netting Arrangement	41,227	34,632
Derivatives Liabilities, Subject to Master Netting Arrangement	45,483	49,290
Derivative, Collateral, Right to Reclaim Securities and/or Cash Held at Third-Party Custodians	$ 12,953	$ 20,109