v3.20.4
Trading Cash Instruments - Fair Value, Cash Instruments, Measurement Inputs, Disclosure (Detail)
$ in Millions
Dec. 31, 2020
USD ($)
yr
Dec. 31, 2019
USD ($)
yr
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total financial assets at fair value | $ $ 627,073 $ 539,568
Level 3 [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total financial assets at fair value | $ 26,305 23,068
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total financial assets at fair value | $ $ 203 $ 191
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.017 0.027
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Recovery Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.051 0.114
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 1.1 0.3
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.220 0.217
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Recovery Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.949 0.811
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 9.1 6.6
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.090 0.135
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Recovery Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.577 0.556
Level 3 [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 5.0 2.8
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total financial assets at fair value | $ $ 131 $ 231
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.006 0.012
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Cumulative Loss Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.034 0.054
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.9 2.3
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.157 0.120
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Cumulative Loss Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.456 0.304
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 16.1 12.4
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.063 0.058
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Cumulative Loss Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.208 0.163
Level 3 [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 6.5 5.7
Level 3 [Member] | Corporate debt instruments [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Total financial assets at fair value | $ $ 797 $ 692
Level 3 [Member] | Corporate debt instruments [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.006 0.001
Level 3 [Member] | Corporate debt instruments [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Recovery Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.000 0.000
Level 3 [Member] | Corporate debt instruments [Member] | Minimum [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.3 1.7
Level 3 [Member] | Corporate debt instruments [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.306 0.204
Level 3 [Member] | Corporate debt instruments [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Recovery Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.736 0.697
Level 3 [Member] | Corporate debt instruments [Member] | Maximum [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 25.5 16.6
Level 3 [Member] | Corporate debt instruments [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Yield [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.095 0.072
Level 3 [Member] | Corporate debt instruments [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Recovery Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 0.587 0.549
Level 3 [Member] | Corporate debt instruments [Member] | Weighted Average [Member] | Fair Value Unobservable Inputs, Duration [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value Unobservable Inputs, Asset 4.0 5.1