Derivatives and Hedging Activities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative [Line Items]
Gross Fair Value of Derivative Asset Contracts Not Enforceable	$ 17,150		$ 9,150
Gross Fair Value of Derivative Liability Contracts Not Enforceable	20,350		14,880
Net Gains / (Losses) on Derivative assets and liabilities	2,440
Net Realized Gains / (Losses) on Derivative assets and liabilities	137	$ 49
Net Unrealized Gains / (Losses) on Derivative assets and liabilities	2,305	$ (91)
Maximum Payout/Notional Amount of Written Credit Derivative	657,117		522,569
Maximum Payout/Notional Amount of Purchased Credit Derivatives	705,200		581,760
Net purchased protection notional value of credit derivatives	48,080		59,190
Foreign Currency Denominated Debt Designated As Foreign Currency Hedge	3,520		3,050
Expected Reduction in Gross Credit Derivative Assets Due to Each Day Settlement			3,970
Expected Reduction in Gross Credit Derivative Liabilities Due to Each Day Settlement			$ 4,150
Market making [Member]
Derivative [Line Items]
Net Gains / (Losses) on Derivative assets and liabilities	2,420
Other Principal Transactions [Member]
Derivative [Line Items]
Net Gains / (Losses) on Derivative assets and liabilities	$ 23