Variable interest entities - Loan Delinquencies and Net Charge-offs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Total assets held by securitization VIEs	$ 239,500		$ 239,500		$ 254,300
Commercial and other
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Total assets held by securitization VIEs	125,600		125,600		129,600
Securitized loans
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
90 days past due	16,791		16,791		19,358
Liquidation losses	1,077	$ 1,289	2,857	$ 4,391
Securitized loans in which the firm has no continuing involvement	53,300		53,300		52,200
Securitized loans | Commercial and other
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
90 days past due	1,580		1,580		1,522
Liquidation losses	211	471	350	1,113
Nonconsolidated entities
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Securitized assets	184,448		184,448		198,391
Nonconsolidated entities | Commercial and other
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Securitized assets	87,369		87,369		94,438
VIEs consolidated by the Firm
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Assets held in consolidated securitization VIEs	1,800		1,800		3,700
VIEs consolidated by the Firm | Commercial and other
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Assets held in consolidated securitization VIEs	200		200		200
Prime / Alt-A & Option ARMs | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Total assets held by securitization VIEs	88,700		88,700		96,300
Prime / Alt-A & Option ARMs | Securitized loans | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
90 days past due	9,481		9,481		11,363
Liquidation losses	486	465	1,402	1,722
Prime / Alt-A & Option ARMs | Nonconsolidated entities | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Securitized assets	73,779		73,779		78,294
Prime / Alt-A & Option ARMs | VIEs consolidated by the Firm | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Assets held in consolidated securitization VIEs	1,500		1,500		2,700
Subprime | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Total assets held by securitization VIEs	25,200		25,200		28,400
Subprime | Securitized loans | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
90 days past due	5,730		5,730		6,473
Liquidation losses	380	$ 353	1,105	$ 1,556
Subprime | Nonconsolidated entities | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Securitized assets	23,300		23,300		25,659
Subprime | VIEs consolidated by the Firm | Residential mortgage
Information about delinquencies, net charge-offs, and components of off-balance sheet securitized financial assets [Abstract]
Assets held in consolidated securitization VIEs	$ 100		$ 100		$ 800