Fair value option - Structured note products by balance sheet classification and risk component (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	$ 50,235	$ 52,829
Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	15,318	13,437
Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	3,351	4,473
Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	2,014	2,378
Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	26,683	29,175
Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	2,869	3,366
Long-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	30,534	30,089
Long-term debt | Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	11,506	10,858
Long-term debt | Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	3,256	4,023
Long-term debt | Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	1,853	2,150
Long-term debt | Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	13,086	12,348
Long-term debt | Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	833	710
Other borrowed funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	8,899	14,177
Other borrowed funds | Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	50	460
Other borrowed funds | Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	95	450
Other borrowed funds | Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	150	211
Other borrowed funds | Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	8,523	12,412
Other borrowed funds | Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	81	644
Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	10,802	8,563
Deposits | Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	3,762	2,119
Deposits | Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	0	0
Deposits | Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	11	17
Deposits | Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	5,074	4,415
Deposits | Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Structured notes balance	$ 1,955	$ 2,012