Allowance for credit losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs/Write-offs of PCI loans			$ 162	$ 196
Provision for credit losses	$ 682	$ 757	2,576	2,299
Loans by impairment methodology
Asset-specific					$ 12,501		$ 15,670
Formula-based					749,552		671,142
PCI					42,240		48,492
Total retained loans					804,293	$ 747,508	735,304
Lending-related commitments by impairment methodology
Asset-specific					176		134
Formula-based					940,610		1,057,070
Total lending-related commitments					940,786	950,997	1,057,204
Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			86	113
Impaired collateral-dependent loans
Loans measured at fair value of collateral less cost to sell					2,978		3,453
Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			14,185	16,264
Gross charge-offs/Write-offs of PCI loans			3,941	4,601
Gross recoveries			(919)	(1,060)
Net charge-offs/(recoveries)			3,022	3,541
Provision for credit losses			2,463	2,368
Other			2	(6)
Ending balance	13,466	14,889	13,466	14,889
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific					1,125		1,242
Formula-based					9,553		9,985
PCI					2,788		3,662
Total allowance for loan losses	13,466	14,889	14,185	16,264	13,466	14,185	14,889
Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			622	705
Provision for credit losses			113	(69)
Other			0	1
Ending balance	735	637	735	637
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Allowance for lending-related commitments by impairment methodology, asset-specific					69		68
Allowance for lending-related commitments by impairment methodology, formula-based					666		569
Total allowance for loan losses	735	637	622	705	735	622	637
Consumer, excluding credit card
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs/Write-offs of PCI loans			162	196
Loans by impairment methodology
Asset-specific					9,817		12,779
Formula-based					279,679		227,113
PCI					42,236		48,487
Total retained loans					331,732	294,979	288,379
Lending-related commitments by impairment methodology
Asset-specific					0		0
Formula-based					60,005		54,912
Total lending-related commitments					60,005		54,912
Consumer, excluding credit card | Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			84	105
Impaired collateral-dependent loans
Loans measured at fair value of collateral less cost to sell					2,653		3,138
Consumer, excluding credit card | Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			7,050	8,456
Gross charge-offs/Write-offs of PCI loans			1,269	1,613
Gross recoveries			(577)	(629)
Net charge-offs/(recoveries)			692	984
Provision for credit losses			(346)	180
Other			(1)	2
Ending balance	5,849	7,458	5,849	7,458
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific					359		618
Formula-based					2,702		3,178
PCI					2,788		3,662
Total allowance for loan losses	5,849	7,458	7,050	8,456	5,849	7,050	7,458
Consumer, excluding credit card | Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			13	8
Provision for credit losses			1	1
Other			0	0
Ending balance	14	9	14	9
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Allowance for lending-related commitments by impairment methodology, asset-specific					0		0
Allowance for lending-related commitments by impairment methodology, formula-based					14		9
Total allowance for loan losses	14	9	13	8	14	13	9
Credit card
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs/Write-offs of PCI loans			0	0
Loans by impairment methodology
Asset-specific					1,563		2,227
Formula-based					124,071		124,337
PCI					0		0
Total retained loans					125,634	128,027	126,564
Lending-related commitments by impairment methodology
Asset-specific					0		0
Formula-based					526,433		531,301
Total lending-related commitments					526,433		531,301
Credit card | Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			0	0
Impaired collateral-dependent loans
Loans measured at fair value of collateral less cost to sell					0		0
Credit card | Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			3,439	3,795
Gross charge-offs/Write-offs of PCI loans			2,626	2,882
Gross recoveries			(278)	(311)
Net charge-offs/(recoveries)			2,348	2,571
Provision for credit losses			2,348	2,371
Other			(5)	(5)
Ending balance	3,434	3,590	3,434	3,590
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific					485		500
Formula-based					2,949		3,090
PCI					0		0
Total allowance for loan losses	3,434	3,590	3,439	3,795	3,434	3,439	3,590
Credit card | Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			0	0
Provision for credit losses			0	0
Other			0	0
Ending balance	0	0	0	0
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Allowance for lending-related commitments by impairment methodology, asset-specific					0		0
Allowance for lending-related commitments by impairment methodology, formula-based					0		0
Total allowance for loan losses	0	0	0	0	0	0	0
Wholesale
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs/Write-offs of PCI loans			0	0
Loans by impairment methodology
Asset-specific					1,121		664
Formula-based					345,802		319,692
PCI					4		5
Total retained loans					346,927	324,502	320,361
Lending-related commitments by impairment methodology
Asset-specific					176		134
Formula-based					354,172		470,857
Total lending-related commitments					354,348		470,991
Wholesale | Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			2	8
Impaired collateral-dependent loans
Loans measured at fair value of collateral less cost to sell					325		315
Wholesale | Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			3,696	4,013
Gross charge-offs/Write-offs of PCI loans			46	106
Gross recoveries			(64)	(120)
Net charge-offs/(recoveries)			(18)	(14)
Provision for credit losses			461	(183)
Other			8	(3)
Ending balance	4,183	3,841	4,183	3,841
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific					281		124
Formula-based					3,902		3,717
PCI					0		0
Total allowance for loan losses	4,183	3,841	3,696	4,013	4,183	3,696	3,841
Wholesale | Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			609	697
Provision for credit losses			112	(70)
Other			0	1
Ending balance	721	628	721	628
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Allowance for lending-related commitments by impairment methodology, asset-specific					69		68
Allowance for lending-related commitments by impairment methodology, formula-based					652		560
Total allowance for loan losses	$ 721	$ 628	$ 609	$ 697	$ 721	$ 609	$ 628