Fair value measurement - Impact of Credit Adjustments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivatives CVA
Impact of credit adjustments on earnings [Abstract]
Derivative credit adjustments	$ (127)	$ (57)	$ 395	$ 196
DVA and FVA
Impact of credit adjustments on earnings [Abstract]
Derivative credit adjustments	(121)	144	(58)	(17)
Structured note credit adjustments	552	161	1,203	340
DVA
Impact of credit adjustments on earnings [Abstract]
Derivative credit adjustments	51	68	108	(27)
Structured note credit adjustments	$ 169	$ 190	$ 492	$ 209