Fair Value Measurement - Level 3 Inputs (Details) $ in Millions	Sep. 30, 2019 USD ($) $ / shares $ / bbl	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	$ 5,760		$ 3,151
MSRs	$ 4,419	$ 5,093	6,130	$ 6,433	$ 6,241	$ 6,030
Assumed par value for price input (in dollars per share) | $ / shares	$ 100
Level 3 | Yield | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	0.12
Level 3 | Yield | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	0.12
Level 3 | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs | $ / shares	18
Level 3 | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs | $ / shares	115
Level 3 | Price (in dollars per share) | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs | $ / shares	36
Level 3 | Interest rate spread volatility | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.0020
Level 3 | Interest rate spread volatility | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.0030
Level 3 | Interest rate correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	(0.28)
Level 3 | Interest rate correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.96
Level 3 | IR-FX correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	(0.58)
Level 3 | IR-FX correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.60
Level 3 | Credit spread | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	0.0045
Level 3 | Credit spread | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	0.0045
Level 3 | Credit spread | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	0.0045
Level 3 | Equity correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.10
Level 3 | Equity correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.98
Level 3 | Equity-FX correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	(0.81)
Level 3 | Equity-FX correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.59
Level 3 | Equity-IR correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.25
Level 3 | Equity-IR correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits, measurement inputs	0.60
Level 3 | Residential mortgage-backed securities and loans | Yield | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0
Level 3 | Residential mortgage-backed securities and loans | Yield | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.19
Level 3 | Residential mortgage-backed securities and loans | Yield | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.05
Level 3 | Residential mortgage-backed securities and loans | Prepayment speed | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0
Level 3 | Residential mortgage-backed securities and loans | Prepayment speed | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.22
Level 3 | Residential mortgage-backed securities and loans | Prepayment speed | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.14
Level 3 | Residential mortgage-backed securities and loans | Conditional default rate | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0
Level 3 | Residential mortgage-backed securities and loans | Conditional default rate | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.04
Level 3 | Residential mortgage-backed securities and loans | Conditional default rate | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.01
Level 3 | Residential mortgage-backed securities and loans | Loss severity | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0
Level 3 | Residential mortgage-backed securities and loans | Loss severity | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	1
Level 3 | Residential mortgage-backed securities and loans | Loss severity | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input	0.02
Level 3 | Commercial mortgage-backed securities and loans | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input | $ / shares	0
Level 3 | Commercial mortgage-backed securities and loans | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input | $ / shares	102
Level 3 | Commercial mortgage-backed securities and loans | Price (in dollars per share) | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input | $ / shares	80
Level 3 | Obligations of U.S. states and municipalities | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	68
Level 3 | Obligations of U.S. states and municipalities | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	100
Level 3 | Obligations of U.S. states and municipalities | Price (in dollars per share) | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	97
Level 3 | Corporate debt securities | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	4
Level 3 | Corporate debt securities | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	116
Level 3 | Corporate debt securities | Price (in dollars per share) | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	79
Level 3 | Loans | Yield | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input	0.05
Level 3 | Loans | Yield | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input	0.22
Level 3 | Loans | Yield | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input	0.07
Level 3 | Loans | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input | $ / shares	12
Level 3 | Loans | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input | $ / shares	101
Level 3 | Loans | Price (in dollars per share) | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input | $ / shares	78
Level 3 | Asset-backed securities | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	1
Level 3 | Asset-backed securities | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	100
Level 3 | Asset-backed securities | Price (in dollars per share) | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	53
Level 3 | Net interest rate derivatives | Prepayment speed | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.04
Level 3 | Net interest rate derivatives | Prepayment speed | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.30
Level 3 | Net interest rate derivatives | Interest rate spread volatility | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.0020
Level 3 | Net interest rate derivatives | Interest rate spread volatility | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.0030
Level 3 | Net interest rate derivatives | Interest rate correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	(0.28)
Level 3 | Net interest rate derivatives | Interest rate correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.96
Level 3 | Net interest rate derivatives | IR-FX correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.53
Level 3 | Net interest rate derivatives | IR-FX correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.60
Level 3 | Net credit derivatives | Conditional default rate | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.02
Level 3 | Net credit derivatives | Conditional default rate | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.93
Level 3 | Net credit derivatives | Loss severity | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	1
Level 3 | Net credit derivatives | Loss severity | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	1.00
Level 3 | Net credit derivatives | Price (in dollars per share) | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	1
Level 3 | Net credit derivatives | Price (in dollars per share) | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	115
Level 3 | Net credit derivatives | Credit correlation | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.30
Level 3 | Net credit derivatives | Credit correlation | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.60
Level 3 | Net credit derivatives | Credit spread | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.0004
Level 3 | Net credit derivatives | Credit spread | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.1315
Level 3 | Net credit derivatives | Recovery rate | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.15
Level 3 | Net credit derivatives | Recovery rate | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.70
Level 3 | Net foreign exchange derivatives | Prepayment speed | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.09
Level 3 | Net foreign exchange derivatives | Prepayment speed | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.09
Level 3 | Net foreign exchange derivatives | IR-FX correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	(0.58)
Level 3 | Net foreign exchange derivatives | IR-FX correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.60
Level 3 | Net equity derivatives | Equity volatility | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.11
Level 3 | Net equity derivatives | Equity volatility | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.82
Level 3 | Net equity derivatives | Equity correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.10
Level 3 | Net equity derivatives | Equity correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.98
Level 3 | Net equity derivatives | Equity-FX correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	(0.81)
Level 3 | Net equity derivatives | Equity-FX correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.59
Level 3 | Net equity derivatives | Equity-IR correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.25
Level 3 | Net equity derivatives | Equity-IR correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.60
Level 3 | Net commodity derivatives | Forward commodity price | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs | $ / bbl	30
Level 3 | Net commodity derivatives | Forward commodity price | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs | $ / bbl	61
Level 3 | Net commodity derivatives | Commodity volatility | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.05
Level 3 | Net commodity derivatives | Commodity volatility | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	1.11
Level 3 | Net commodity derivatives | Commodity correlation | Option pricing | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	(0.48)
Level 3 | Net commodity derivatives | Commodity correlation | Option pricing | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.95
Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	$ 5,760		3,151
MSRs	4,419		6,130
Long-term debt, short-term borrowings, and deposits	249,535		234,238
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	1		122
MSRs	4,419		6,130
Long-term debt, short-term borrowings, and deposits	38,638		$ 34,784
Other level 3 asset and liabilities, net	229
Recurring | Level 3 | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
MSRs	4,419
Other assets	303
Recurring | Level 3 | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets	775
Recurring | Level 3 | Option pricing
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt, short-term borrowings, and deposits	27,986
Recurring | Level 3 | Residential mortgage-backed securities and loans | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	1,132
Recurring | Level 3 | Commercial mortgage-backed securities and loans | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	147
Recurring | Level 3 | Obligations of U.S. states and municipalities | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading	627
Recurring | Level 3 | Corporate debt securities | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading	484
Recurring | Level 3 | Loans | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	194
Recurring | Level 3 | Loans | Discounted cash flows | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	297
Recurring | Level 3 | Loans | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	1,115
Recurring | Level 3 | Loans | Market comparables | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	141
Recurring | Level 3 | Asset-backed securities | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading	38
Recurring | Level 3 | Net interest rate derivatives | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	69
Recurring | Level 3 | Net interest rate derivatives | Option pricing
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	(388)
Recurring | Level 3 | Net credit derivatives | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	(353)
Recurring | Level 3 | Net credit derivatives | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	36
Recurring | Level 3 | Net foreign exchange derivatives | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	(162)
Recurring | Level 3 | Net foreign exchange derivatives | Option pricing
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	(679)
Recurring | Level 3 | Net equity derivatives | Option pricing
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	(3,468)
Recurring | Level 3 | Net commodity derivatives | Option pricing
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability)	(47)
Recurring | Level 3 | Mortgage-backed securities, U.S. GSEs and government agencies | Discounted cash flows | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	811
Recurring | Level 3 | Residential mortgage-backed securities | Discounted cash flows | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	24
Recurring | Level 3 | Commercial | Market comparables | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	5
Recurring | Level 3 | Nontrading loans | Market comparables | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	$ 1