Fair Value Measurement - Level 3 Inputs (Details) $ in Millions	Sep. 30, 2018 USD ($) $ / shares $ / bbl	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	$ 2,987		$ 2,508
Asset-backed securities	200,030		201,678
MSRs	$ 6,433	$ 6,241	6,030	$ 5,738	$ 5,753	$ 6,096
Assumed par value for price input (in dollars per share) | $ / shares	$ 100
Obligations of U.S. states and municipalities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	$ 38,121		32,338
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	2,056		2,757
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	27,913
Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	$ 7,048		5,025
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	0.08
Level 3 | Yield | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	0.10
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	0.08
Level 3 | Price | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs | $ / shares	34
Level 3 | Price | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs | $ / shares	106
Level 3 | Price | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs | $ / shares	45
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	0.0070
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	0.0070
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	0.0070
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	0.0016
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	0.0038
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	(0.45)
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	0.97
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	(0.45)
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 | 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	0.95
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	(0.75)
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	0.60
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	0.20
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 | EBITDA multiple | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	3.0
Level 3 | EBITDA multiple | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	9.2
Level 3 | EBITDA multiple | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets, measurement inputs	8.4
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	0.28
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	0.06
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	0.39
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	0.09
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	0.06
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	0.05
Level 3 | Commercial mortgage-backed securities and loans | Price | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input | $ / shares	4
Level 3 | Commercial mortgage-backed securities and loans | Price | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans, measurement input | $ / shares	101
Level 3 | Commercial mortgage-backed securities and loans | Price | 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	93
Level 3 | Obligations of U.S. states and municipalities | Price | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	60
Level 3 | Obligations of U.S. states and municipalities | Price | 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 | 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 | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	3
Level 3 | Corporate debt securities | Price | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	110
Level 3 | Corporate debt securities | Price | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	80
Level 3 | Asset-backed securities | Prepayment speed | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.20
Level 3 | Asset-backed securities | Prepayment speed | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.20
Level 3 | Asset-backed securities | Prepayment speed | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.20
Level 3 | Asset-backed securities | Conditional default rate | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.02
Level 3 | Asset-backed securities | Conditional default rate | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.02
Level 3 | Asset-backed securities | Conditional default rate | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.02
Level 3 | Asset-backed securities | Loss severity | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.30
Level 3 | Asset-backed securities | Loss severity | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.30
Level 3 | Asset-backed securities | Loss severity | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.30
Level 3 | Asset-backed securities | Price | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	0
Level 3 | Asset-backed securities | Price | 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 | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities, trading, measurement input | $ / shares	51
Level 3 | Asset-backed securities | Credit spread | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.0219
Level 3 | Asset-backed securities | Credit spread | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.0219
Level 3 | Asset-backed securities | Credit spread | Discounted cash flows | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities, measurement inputs	0.0219
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
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	0.0016
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	0.0038
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	(0.45)
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	0.97
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	0.55
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 | Yield | Discounted cash flows | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.03
Level 3 | Net credit derivatives | Yield | Discounted cash flows | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	0.52
Level 3 | Net credit 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	0.05
Level 3 | Net credit 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	0.17
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
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	1
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	0
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
Level 3 | Net credit derivatives | Price | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	10
Level 3 | Net credit derivatives | Price | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net derivative asset (liability), measurement inputs	98
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	0.0006
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	0.1543
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	0.35
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 | 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	0.20
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	0.08
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	(0.45)
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	0.10
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	0.60
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	0.95
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	(0.75)
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	0.60
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	0.20
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	61
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	83
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	0.48
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	(0.52)
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
Level 3 | Trading loans | Price | Market comparables | Minimum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input | $ / shares	3
Level 3 | Trading loans | Price | Market comparables | Maximum
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input | $ / shares	102
Level 3 | Trading loans | Price | Market comparables | Weighted average
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans, measurement input | $ / shares	79
Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	$ 2,987		2,508
Asset-backed securities	200,030
MSRs	6,433		6,030
Long-term debt, short-term borrowings, and deposits	239,882		211,644
Recurring | Obligations of U.S. states and municipalities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	38,121
Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	2,056
Recurring | Mortgage-backed securities, U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	63,110
Recurring | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	9,217
Recurring | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	7,048
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	140		276
Asset-backed securities	62
MSRs	6,433		6,030
Long-term debt, short-term borrowings, and deposits	36,049		$ 32,271
Other level 3 asset and liabilities, net	384
Recurring | Level 3 | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
MSRs	6,433
Other assets	322
Recurring | Level 3 | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Other assets	1,154
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	26,449
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	823
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	439
Recurring | Level 3 | Obligations of U.S. states and municipalities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	0
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	699
Recurring | Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	0
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	395
Recurring | Level 3 | Asset-backed securities | Discounted cash flows
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	61
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	76
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)	163
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)	528
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)	26
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)	1
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)	(181)
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)	(121)
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)	(2,277)
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)	(525)
Recurring | Level 3 | Mortgage-backed securities, U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	0
Recurring | Level 3 | Mortgage-backed securities, U.S. 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	502
Recurring | Level 3 | Mortgage-backed securities, U.S. government agencies | Market comparables | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	27
Recurring | Level 3 | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	1
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	78
Recurring | Level 3 | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Asset-backed securities	0
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	13
Recurring | Level 3 | Trading 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	243
Recurring | Level 3 | Trading loans | Market comparables
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans	1,031
Recurring | Level 3 | Trading loans | Market comparables | Commercial
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities and loans	259
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	$ 140