Derivative Instruments - Credit Derivatives (Details 4a) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Total credit derivatives and credit-related notes
Protection sold	$ (3,269,347)	$ (3,021,182)
Protection purchased with identical underlyings	(3,177,391)	(2,884,754)
Net protection (sold)/purchased	91,956	136,428
Other protection purchased	46,141	78,889
Total credit derivatives
Total credit derivatives and credit-related notes
Protection sold	(3,269,153)	(3,020,949)
Protection purchased with identical underlyings	(3,177,391)	(2,884,754)
Net protection (sold)/purchased	91,762	136,195
Other protection purchased	42,566	75,634
Credit default swaps
Total credit derivatives and credit-related notes
Protection sold	(3,191,033)	(2,954,705)
Protection purchased with identical underlyings	(3,158,710)	(2,879,105)
Net protection (sold)/purchased	32,323	75,600
Other protection purchased	12,971	42,460
Other credit derivatives
Total credit derivatives and credit-related notes
Protection sold	(78,120)	(66,244)
Protection purchased with identical underlyings	(18,681)	(5,649)
Net protection (sold)/purchased	59,439	60,595
Other protection purchased	29,595	33,174
Credit-related notes
Total credit derivatives and credit-related notes
Protection sold	(194)	(233)
Protection purchased with identical underlyings	0	0
Net protection (sold)/purchased	194	233
Other protection purchased	$ 3,575	$ 3,255