v3.20.4
Trading Cash Instruments - Cash Instruments by Level (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Trading Cash Instruments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total Trading Assets $ 324,049 $ 310,080
Trading cash instruments assets | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 216,370 222,413
Trading cash instruments assets | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 106,442 86,425
Trading cash instruments assets | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 1,237 1,242
Trading cash instruments assets | U.S. Government and Agency Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 138,533 142,935
Trading cash instruments assets | U.S. Government and Agency Obligations [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 93,670 108,200
Trading cash instruments assets | U.S. Government and Agency Obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 44,863 34,714
Trading cash instruments assets | U.S. Government and Agency Obligations [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value   21
Trading cash instruments assets | Non-U.S. Government and Agency Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 57,423 44,839
Trading cash instruments assets | Non-U.S. Government and Agency Obligations [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 46,147 33,709
Trading cash instruments assets | Non-U.S. Government and Agency Obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 11,261 11,108
Trading cash instruments assets | Non-U.S. Government and Agency Obligations [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 15 22
Trading cash instruments assets | Loans and Securities Backed by Commercial Real Estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 800 2,222
Trading cash instruments assets | Loans and Securities Backed by Commercial Real Estate [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 597 2,031
Trading cash instruments assets | Loans and Securities Backed by Commercial Real Estate [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 203 191
Trading cash instruments assets | Loans and Securities Backed by Residential Real Estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 7,079 6,025
Trading cash instruments assets | Loans and Securities Backed by Residential Real Estate [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 6,948 5,794
Trading cash instruments assets | Loans and Securities Backed by Residential Real Estate [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 131 231
Trading cash instruments assets | Corporate debt instruments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 31,351 28,773
Trading cash instruments assets | Corporate debt instruments [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 915 1,313
Trading cash instruments assets | Corporate debt instruments [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 29,639 26,768
Trading cash instruments assets | Corporate debt instruments [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 797 692
Trading cash instruments assets | State and Municipal Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 200 680
Trading cash instruments assets | State and Municipal Obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 200 680
Trading cash instruments assets | Other debt obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 1,412 1,493
Trading cash instruments assets | Other debt obligations [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 338 409
Trading cash instruments assets | Other debt obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 1,055 1,074
Trading cash instruments assets | Other debt obligations [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 19 10
Trading cash instruments assets | Equity Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 77,877 79,346
Trading cash instruments assets | Equity Securities [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 75,300 78,782
Trading cash instruments assets | Equity Securities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 2,505 489
Trading cash instruments assets | Equity Securities [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 72 75
Trading cash instruments assets | Commodities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 9,374 3,767
Trading cash instruments assets | Commodities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Assets at Fair Value 9,374 3,767
Cash Instruments Liabilities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (95,136) (65,033)
Cash Instruments Liabilities [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (84,708) (54,761)
Cash Instruments Liabilities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (10,348) (9,999)
Cash Instruments Liabilities [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (80) (273)
Cash Instruments Liabilities [Member] | U.S. Government and Agency Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (16,893) (9,961)
Cash Instruments Liabilities [Member] | U.S. Government and Agency Obligations [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (16,880) (9,914)
Cash Instruments Liabilities [Member] | U.S. Government and Agency Obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (13) (47)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (23,884) (23,424)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (22,092) (21,213)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (1,792) (2,205)
Cash Instruments Liabilities [Member] | Non-U.S. Government and Agency Obligations [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value   (6)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Commercial Real Estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (18) (32)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (17) (31)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Commercial Real Estate [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (1) (1)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Residential Real Estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (1) (2)
Cash Instruments Liabilities [Member] | Loans and Securities Backed by Residential Real Estate [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (1) (2)
Cash Instruments Liabilities [Member] | Corporate debt instruments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (8,022) (7,862)
Cash Instruments Liabilities [Member] | Corporate debt instruments [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (2) (115)
Cash Instruments Liabilities [Member] | Corporate debt instruments [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (7,970) (7,494)
Cash Instruments Liabilities [Member] | Corporate debt instruments [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (50) (253)
Cash Instruments Liabilities [Member] | State and Municipal Obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (5) (2)
Cash Instruments Liabilities [Member] | State and Municipal Obligations [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (5) (2)
Cash Instruments Liabilities [Member] | Other debt obligations [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (2)  
Cash Instruments Liabilities [Member] | Other debt obligations [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (2)  
Cash Instruments Liabilities [Member] | Equity Securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (46,311) (23,744)
Cash Instruments Liabilities [Member] | Equity Securities [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (45,734) (23,519)
Cash Instruments Liabilities [Member] | Equity Securities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value (550) (212)
Cash Instruments Liabilities [Member] | Equity Securities [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value $ (27) (13)
Cash Instruments Liabilities [Member] | Commodities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value   (6)
Cash Instruments Liabilities [Member] | Commodities [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading Cash Instruments Liabilities at Fair Value   $ (6)