Collateralized Agreements and Financings - Assets pledged as collateral (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Collateralized Agreements And Financings [Abstract]
Trading assets owned pledged in connection with repurchase agreements, securities lending agreements and other secured financings to counterparties that had the right to deliver or repledge	$ 80,268	$ 66,605
Investments pledged to counterparties that Had the right to deliver or repledge	14,244	10,968
Trading assets owned pledged in connection with repurchase agreements, securities lending agreements and other secured financings to counterparties that did not have right to deliver or repledge	110,700	101,578
Investments pledged to counterparties that did not have the right to deliver or repledge	2,825	849
Loans pledged to counterparties that do not have the right to deliver or repledge	8,076	6,628
Other assets (substantially all real estate and cash) owned and pledged in connection with other secured financings to counterparties that did not have the right to deliver or repledge	$ 15,488	$ 12,337