Derivative instruments - Credit Derivatives (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Total credit derivatives and credit-related notes
Protection sold	$ (1,728,245)	$ (2,100,303)
Protection purchased with identical underlyings	1,741,678	2,110,144
Net protection (sold)/purchased	13,433	9,841
Other protection purchased	37,146	41,810
Total credit derivatives
Total credit derivatives and credit-related notes
Protection sold	(1,728,223)	(2,100,263)
Protection purchased with identical underlyings	1,741,678	2,110,144
Net protection (sold)/purchased	13,455	9,881
Other protection purchased	32,789	38,106
Credit default swaps
Total credit derivatives and credit-related notes
Protection sold	(1,683,730)	(2,056,982)
Protection purchased with identical underlyings	1,699,718	2,078,096
Net protection (sold)/purchased	15,988	21,114
Other protection purchased	14,572	18,631
Other credit derivatives
Total credit derivatives and credit-related notes
Protection sold	(44,493)	(43,281)
Protection purchased with identical underlyings	41,960	32,048
Net protection (sold)/purchased	(2,533)	(11,233)
Other protection purchased	18,217	19,475
Credit-related notes
Total credit derivatives and credit-related notes
Protection sold	(22)	(40)
Protection purchased with identical underlyings	0	0
Net protection (sold)/purchased	(22)	(40)
Other protection purchased	$ 4,357	$ 3,704