Derivative Instruments - Credit Derivatives (Details 4a) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Total credit derivatives and credit-related notes
Protection sold	$ (3,155,918)	$ (3,021,182)
Protection purchased with identical underlyings	3,097,369	2,884,754
Net protection (sold)/purchased	(58,549)	(136,428)
Other protection purchased	40,480	78,889
Total credit derivatives
Total credit derivatives and credit-related notes
Protection sold	(3,155,769)	(3,020,949)
Protection purchased with identical underlyings	3,097,369	2,884,754
Net protection (sold)/purchased	(58,400)	(136,195)
Other protection purchased	38,204	75,634
Credit default swaps
Total credit derivatives and credit-related notes
Protection sold	(3,078,623)	(2,954,705)
Protection purchased with identical underlyings	3,076,709	2,879,105
Net protection (sold)/purchased	(1,914)	(75,600)
Other protection purchased	8,653	42,460
Other credit derivatives
Total credit derivatives and credit-related notes
Protection sold	(77,146)	(66,244)
Protection purchased with identical underlyings	20,660	5,649
Net protection (sold)/purchased	(56,486)	(60,595)
Other protection purchased	29,551	33,174
Credit-related notes
Total credit derivatives and credit-related notes
Protection sold	(149)	(233)
Protection purchased with identical underlyings	0	0
Net protection (sold)/purchased	(149)	(233)
Other protection purchased	$ 2,276	$ 3,255