Fair Value Option - Structured note products by balance sheet classification and risk component (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	$ 80,724	$ 74,798
Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	36,571	30,183
Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	5,004	5,641
Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	3,364	3,026
Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	34,172	31,235
Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	1,613	4,713
Long-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	53,069	47,037
Long-term debt | Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	24,137	22,056
Long-term debt | Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	4,009	4,329
Long-term debt | Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	3,169	2,841
Long-term debt | Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	21,382	17,581
Long-term debt | Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	372	230
Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	6,670	8,649
Short-term borrowings | Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	62	69
Short-term borrowings | Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	995	1,312
Short-term borrowings | Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	157	147
Short-term borrowings | Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	5,422	7,106
Short-term borrowings | Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	34	15
Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	20,985	19,112
Deposits | Interest rate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	12,372	8,058
Deposits | Credit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	0	0
Deposits | Foreign exchange
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	38	38
Deposits | Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	7,368	6,548
Deposits | Commodity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total structured notes	$ 1,207	$ 4,468