Derivative instruments - Impact on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Gross derivative receivables	$ 1,055,096	$ 1,328,428
Net derivative receivables	68,668	78,975
Gross derivative payables	1,037,512	1,310,773
Net derivative payables	57,140	71,116
Interest rate
Derivatives, Fair Value [Line Items]
Gross derivative receivables	738,951	950,257
Net derivative receivables	29,116	33,725
Gross derivative payables	701,839	918,379
Net derivative payables	10,725	17,745
Credit
Derivatives, Fair Value [Line Items]
Gross derivative receivables	54,409	76,842
Net derivative receivables	1,724	1,838
Gross derivative payables	53,111	75,895
Net derivative payables	1,646	1,593
Foreign exchange
Derivatives, Fair Value [Line Items]
Gross derivative receivables	186,549	215,187
Net derivative receivables	21,116	21,253
Gross derivative payables	202,453	224,614
Net derivative payables	22,044	22,970
Equity
Derivatives, Fair Value [Line Items]
Gross derivative receivables	46,727	42,489
Net derivative receivables	7,490	8,177
Gross derivative payables	47,549	46,262
Net derivative payables	9,006	11,740
Commodity
Derivatives, Fair Value [Line Items]
Gross derivative receivables	28,460	43,653
Net derivative receivables	9,222	13,982
Gross derivative payables	32,560	45,623
Net derivative payables	13,719	17,068
Not designated as hedges
Derivatives, Fair Value [Line Items]
Gross derivative receivables	1,047,512	1,318,904
Gross derivative payables	1,033,548	1,306,968
Not designated as hedges | Interest rate
Derivatives, Fair Value [Line Items]
Gross derivative receivables	733,909	944,885
Gross derivative payables	699,048	915,368
Not designated as hedges | Credit
Derivatives, Fair Value [Line Items]
Gross derivative receivables	54,409	76,842
Gross derivative payables	53,111	75,895
Not designated as hedges | Foreign exchange
Derivatives, Fair Value [Line Items]
Gross derivative receivables	185,015	211,537
Gross derivative payables	201,298	223,988
Not designated as hedges | Equity
Derivatives, Fair Value [Line Items]
Gross derivative receivables	46,727	42,489
Gross derivative payables	47,549	46,262
Not designated as hedges | Commodity
Derivatives, Fair Value [Line Items]
Gross derivative receivables	27,452	43,151
Gross derivative payables	32,542	45,455
Designated as hedges
Derivatives, Fair Value [Line Items]
Gross derivative receivables	7,584	9,524
Gross derivative payables	3,964	3,805
Designated as hedges | Interest rate
Derivatives, Fair Value [Line Items]
Gross derivative receivables	5,042	5,372
Gross derivative payables	2,791	3,011
Designated as hedges | Credit
Derivatives, Fair Value [Line Items]
Gross derivative receivables	0	0
Gross derivative payables	0	0
Designated as hedges | Foreign exchange
Derivatives, Fair Value [Line Items]
Gross derivative receivables	1,534	3,650
Gross derivative payables	1,155	626
Designated as hedges | Equity
Derivatives, Fair Value [Line Items]
Gross derivative receivables	0	0
Gross derivative payables	0	0
Designated as hedges | Commodity
Derivatives, Fair Value [Line Items]
Gross derivative receivables	1,008	502
Gross derivative payables	$ 18	$ 168