Derivative instruments - Derivatives Netting (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	$ 1,038,106	$ 1,307,711
Amounts netted on the Consolidated balance sheets	(986,428)	(1,249,453)
Net derivative receivables	51,678	58,258
Derivative receivables where an appropriate legal opinion has not been either sought or obtained	16,990	20,717
Total derivative receivables recognized on the Consolidated balance sheets, Gross derivative receivables	1,055,096	1,328,428
Total derivative receivables recognized on the Consolidated balance sheets, Net derivative receivables	68,668	78,975
Net cash collateral payables	74,300	74,000
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	1,024,161	1,291,703
Amounts netted on the Consolidated balance sheets	(980,372)	(1,239,657)
Net derivative payables	43,789	52,046
Derivative payables where an appropriate legal opinion has not been either sought or obtained	13,351	19,070
Total derivative payables recognized on the Consolidated balance sheets, Gross derivative payables	1,037,512	1,310,773
Total derivative payables recognized on the Consolidated balance sheets, Net derivative payables	57,140	71,116
Netted cash collateral receivables	68,200	64,200
Interest rate contracts
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	732,425	943,763
Amounts netted on the Consolidated balance sheets	(709,835)	(916,532)
Net derivative receivables	22,590	27,231
Total derivative receivables recognized on the Consolidated balance sheets, Gross derivative receivables	738,951	950,257
Total derivative receivables recognized on the Consolidated balance sheets, Net derivative receivables	29,116	33,725
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	700,542	914,422
Amounts netted on the Consolidated balance sheets	(691,114)	(900,634)
Net derivative payables	9,428	13,788
Total derivative payables recognized on the Consolidated balance sheets, Gross derivative payables	701,839	918,379
Total derivative payables recognized on the Consolidated balance sheets, Net derivative payables	10,725	17,745
Interest rate contracts | OTC
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	455,022	542,107
Amounts netted on the Consolidated balance sheets	(432,456)	(514,914)
Net derivative receivables	22,566	27,193
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	431,744	515,904
Amounts netted on the Consolidated balance sheets	(422,367)	(503,384)
Net derivative payables	9,377	12,520
Interest rate contracts | OTC-cleared
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	277,403	401,656
Amounts netted on the Consolidated balance sheets	(277,379)	(401,618)
Net derivative receivables	24	38
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	268,798	398,518
Amounts netted on the Consolidated balance sheets	(268,747)	(397,250)
Net derivative payables	51	1,268
Interest rate contracts | Exchange-traded
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative receivables	0	0
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative payables	0	0
Credit contracts
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	52,759	75,956
Amounts netted on the Consolidated balance sheets	(52,685)	(75,004)
Net derivative receivables	74	952
Total derivative receivables recognized on the Consolidated balance sheets, Gross derivative receivables	54,409	76,842
Total derivative receivables recognized on the Consolidated balance sheets, Net derivative receivables	1,724	1,838
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	52,680	74,830
Amounts netted on the Consolidated balance sheets	(51,465)	(74,302)
Net derivative payables	1,215	528
Total derivative payables recognized on the Consolidated balance sheets, Gross derivative payables	53,111	75,895
Total derivative payables recognized on the Consolidated balance sheets, Net derivative payables	1,646	1,593
Credit contracts | OTC
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	44,739	66,636
Amounts netted on the Consolidated balance sheets	(44,680)	(65,720)
Net derivative receivables	59	916
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	45,435	65,432
Amounts netted on the Consolidated balance sheets	(44,220)	(64,904)
Net derivative payables	1,215	528
Credit contracts | OTC-cleared
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	8,020	9,320
Amounts netted on the Consolidated balance sheets	(8,005)	(9,284)
Net derivative receivables	15	36
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	7,245	9,398
Amounts netted on the Consolidated balance sheets	(7,245)	(9,398)
Net derivative payables	0	0
Foreign exchange contracts
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	181,380	208,839
Amounts netted on the Consolidated balance sheets	(165,433)	(193,934)
Net derivative receivables	15,947	14,905
Total derivative receivables recognized on the Consolidated balance sheets, Gross derivative receivables	186,549	215,187
Total derivative receivables recognized on the Consolidated balance sheets, Net derivative receivables	21,116	21,253
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	197,124	218,064
Amounts netted on the Consolidated balance sheets	(180,409)	(201,644)
Net derivative payables	16,715	16,420
Total derivative payables recognized on the Consolidated balance sheets, Gross derivative payables	202,453	224,614
Total derivative payables recognized on the Consolidated balance sheets, Net derivative payables	22,044	22,970
Foreign exchange contracts | OTC
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	181,104	208,803
Amounts netted on the Consolidated balance sheets	(165,157)	(193,900)
Net derivative receivables	15,947	14,903
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	196,762	217,998
Amounts netted on the Consolidated balance sheets	(180,048)	(201,578)
Net derivative payables	16,714	16,420
Foreign exchange contracts | OTC-cleared
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	276	36
Amounts netted on the Consolidated balance sheets	(276)	(34)
Net derivative receivables	0	2
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	362	66
Amounts netted on the Consolidated balance sheets	(361)	(66)
Net derivative payables	1	0
Foreign exchange contracts | Exchange-traded
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative receivables	0	0
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative payables	0	0
Equity contracts
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	44,088	37,098
Amounts netted on the Consolidated balance sheets	(39,237)	(34,312)
Net derivative receivables	4,851	2,786
Total derivative receivables recognized on the Consolidated balance sheets, Gross derivative receivables	46,727	42,489
Total derivative receivables recognized on the Consolidated balance sheets, Net derivative receivables	7,490	8,177
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	43,670	40,772
Amounts netted on the Consolidated balance sheets	(38,543)	(34,522)
Net derivative payables	5,127	6,250
Total derivative payables recognized on the Consolidated balance sheets, Gross derivative payables	47,549	46,262
Total derivative payables recognized on the Consolidated balance sheets, Net derivative payables	9,006	11,740
Equity contracts | OTC
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	26,509	23,258
Amounts netted on the Consolidated balance sheets	(25,732)	(22,826)
Net derivative receivables	777	432
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	28,605	27,908
Amounts netted on the Consolidated balance sheets	(25,038)	(23,036)
Net derivative payables	3,567	4,872
Equity contracts | OTC-cleared
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative receivables	0	0
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative payables	0	0
Equity contracts | Exchange-traded
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	17,579	13,840
Amounts netted on the Consolidated balance sheets	(13,505)	(11,486)
Net derivative receivables	4,074	2,354
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	15,065	12,864
Amounts netted on the Consolidated balance sheets	(13,505)	(11,486)
Net derivative payables	1,560	1,378
Commodity contracts
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	27,454	42,055
Amounts netted on the Consolidated balance sheets	(19,238)	(29,671)
Net derivative receivables	8,216	12,384
Total derivative receivables recognized on the Consolidated balance sheets, Gross derivative receivables	28,460	43,653
Total derivative receivables recognized on the Consolidated balance sheets, Net derivative receivables	9,222	13,982
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	30,145	43,615
Amounts netted on the Consolidated balance sheets	(18,841)	(28,555)
Net derivative payables	11,304	15,060
Total derivative payables recognized on the Consolidated balance sheets, Gross derivative payables	32,560	45,623
Total derivative payables recognized on the Consolidated balance sheets, Net derivative payables	13,719	17,068
Commodity contracts | OTC
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	14,610	22,555
Amounts netted on the Consolidated balance sheets	(6,644)	(14,327)
Net derivative receivables	7,966	8,228
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	17,490	25,129
Amounts netted on the Consolidated balance sheets	(6,247)	(13,211)
Net derivative payables	11,243	11,918
Commodity contracts | OTC-cleared
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative receivables	0	0
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	0	0
Amounts netted on the Consolidated balance sheets	0	0
Net derivative payables	0	0
Commodity contracts | Exchange-traded
Gross and Net Derivative Receivables by Contract and Settlement Type:
Gross derivative receivables	12,844	19,500
Amounts netted on the Consolidated balance sheets	(12,594)	(15,344)
Net derivative receivables	250	4,156
Gross and Net Derivative Payables by Contract and Settlement Type:
Gross derivative payables	12,655	18,486
Amounts netted on the Consolidated balance sheets	(12,594)	(15,344)
Net derivative payables	$ 61	$ 3,142