Allowance for credit losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	$ 935	$ 692	$ 1,894	$ 1,542
Loans by Impairment Methodology [Abstract]
Asset-specific	12,553	16,390
Formula-based	723,342	668,856
PCI	43,810	50,123
Retained loans	779,705	735,369			$ 747,508
Lending-related commitments by impairment methodology
Asset-specific	133	122
Formula-based	935,449	1,041,251
Total lending-related commitments	935,582	1,041,373			950,997
Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			35	76
Impaired Collateral Dependent Loans [Abstract]
Loans measured at fair value of collateral less cost to sell	3,002	3,571
Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			14,185	16,264
Gross charge-offs			2,636	3,143
Gross (recoveries)			(577)	(716)
Net charge-offs/(recoveries)			2,059	2,427
Provision for credit losses			1,896	1,599
Other			3	(1)
Allowance for credit losses, ending balance	13,915	15,326	13,915	15,326
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific	1,101	1,319
Formula-based	9,599	10,258
PCI	3,215	3,749
Total allowance for loan losses	13,915	15,326	14,185	16,264	14,185
Allowance for loan losses | Purchased Credit-Impaired
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs			110	109
Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			622	705
Provision for credit losses			(2)	(57)
Other			0	0
Allowance for credit losses, ending balance	620	648	620	648
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Allowance for lending-related commitments by impairment methodology, asset-specific	55	43
Allowance for lending-related commitments by impairment methodology, formula-based	565	605
Total allowance for loan losses	620	648	622	705	622
Consumer, excluding credit card
Loans by Impairment Methodology [Abstract]
Asset-specific	9,960	13,191
Formula-based	263,015	224,905
PCI	43,806	50,118
Retained loans	316,781	288,214			294,979
Lending-related commitments by impairment methodology
Asset-specific	0	0
Formula-based	59,817	56,410
Total lending-related commitments	59,817	56,410
Consumer, excluding credit card | Purchased Credit-Impaired
Loans by Impairment Methodology [Abstract]
Retained loans	43,806				46,696
Consumer, excluding credit card | Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			33	81
Impaired Collateral Dependent Loans [Abstract]
Loans measured at fair value of collateral less cost to sell	2,695	3,250
Consumer, excluding credit card | Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			7,050	8,456
Gross charge-offs			827	1,084
Gross (recoveries)			(337)	(399)
Net charge-offs/(recoveries)			490	685
Provision for credit losses			42	81
Other			0	0
Allowance for credit losses, ending balance	6,492	7,743	6,492	7,743
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific	436	598
Formula-based	2,841	3,396
PCI	3,215	3,749
Total allowance for loan losses	6,492	7,743	7,050	8,456	7,050
Consumer, excluding credit card | Allowance for loan losses | Purchased Credit-Impaired
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs			110	109
Consumer, excluding credit card | Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			13	8
Provision for credit losses			2	1
Other			0	0
Allowance for credit losses, ending balance	15	9	15	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	15	9
Total allowance for loan losses	15	9	13	8	13
Credit card
Loans by Impairment Methodology [Abstract]
Asset-specific	1,685	2,467
Formula-based	123,020	123,154
PCI	0	0
Retained loans	124,705	125,621			128,027
Lending-related commitments by impairment methodology
Asset-specific	0	0
Formula-based	523,717	533,688
Total lending-related commitments	523,717	533,688
Credit card | Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			0	0
Impaired Collateral Dependent Loans [Abstract]
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]
Allowance for credit losses, beginning balance			3,439	3,795
Gross charge-offs			1,776	1,982
Gross (recoveries)			(187)	(209)
Net charge-offs/(recoveries)			1,589	1,773
Provision for credit losses			1,589	1,573
Other			(5)	(1)
Allowance for credit losses, ending balance	3,434	3,594	3,434	3,594
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific	518	583
Formula-based	2,916	3,011
PCI	0	0
Total allowance for loan losses	3,434	3,594	3,439	3,795	3,439
Credit card | Allowance for loan losses | Purchased Credit-Impaired
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs			0	0
Credit card | Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			0	0
Provision for credit losses			0	0
Other			0	0
Allowance for credit losses, 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
Wholesale
Loans by Impairment Methodology [Abstract]
Asset-specific	908	732
Formula-based	337,307	320,797
PCI	4	5
Retained loans	338,219	321,534			324,502
Lending-related commitments by impairment methodology
Asset-specific	133	122
Formula-based	351,915	451,153
Total lending-related commitments	352,048	451,275
Wholesale | Impaired collateral-dependent loans
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs/(recoveries)			2	(5)
Impaired Collateral Dependent Loans [Abstract]
Loans measured at fair value of collateral less cost to sell	307	321
Wholesale | Allowance for loan losses
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			3,696	4,013
Gross charge-offs			33	77
Gross (recoveries)			(53)	(108)
Net charge-offs/(recoveries)			(20)	(31)
Provision for credit losses			265	(55)
Other			8	0
Allowance for credit losses, ending balance	3,989	3,989	3,989	3,989
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Asset-specific	147	138
Formula-based	3,842	3,851
PCI	0	0
Total allowance for loan losses	3,989	3,989	3,696	4,013	3,696
Wholesale | Allowance for loan losses | Purchased Credit-Impaired
Allowance for Loan and Lease Losses [Roll Forward]
Gross charge-offs			0	0
Wholesale | Allowance for lending-related commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning balance			609	697
Provision for credit losses			(4)	(58)
Other			0	0
Allowance for credit losses, ending balance	605	639	605	639
Allowance For Lending Related Commitments, by Impairment Methodology [Abstract]
Allowance for lending-related commitments by impairment methodology, asset-specific	55	43
Allowance for lending-related commitments by impairment methodology, formula-based	550	596
Total allowance for loan losses	$ 605	$ 639	$ 609	$ 697	$ 609