Trading Assets and Liabilities - Summary of Trading Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Trading Assets	$ 392,998	$ 393,630
Trading Liabilities	204,269	153,727
Trading Cash Instruments [Member]
Trading Cash Instruments	321,415	324,049
Trading Liabilities	150,763	95,136
Derivatives [Member]
Trading Assets at Fair Value	71,583	69,581
Trading Liabilities	$ 53,506	$ 58,591

The carrying amount of liabilities as of the balance sheet date that pertain to principal and customer trading transactions, or which may be incurred with the objective of generating a profit from short-term fluctuations in price as part of an entity's market-making, hedging and proprietary trading. Examples include short positions in securities, derivatives and commodities, obligations under repurchase agreements, and securities borrowed arrangements.

No definition available.

Name:	us-gaap_TradingLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant