Variable Interest Entities - Consolidated Variable Interest Entities (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 153,201		$ 133,546	$ 94,094	$ 130,547
Trading assets	408,400		355,332
Investments	80,792		63,937
Loans	111,843		108,904
Other assets	37,974		34,882
Total assets	1,132,059	$ 1,141,523	992,968
Liabilities
Other secured financings	24,981		19,277
Customer and other payables	187,357		174,817
Trading liabilities	162,141		108,835
Unsecured short-term borrowings	48,028		48,287
Unsecured long-term borrowings	213,936		207,076
Other liabilities	23,165		21,651
Total liabilities	1,039,409	$ 1,051,494	902,703
Real Estate, Credit-Related and Other Investing [Member]
Assets
Cash and cash equivalents	208		112
Trading assets	3		26
Investments	846		835
Loans	2,077		2,392
Other assets	1,066		1,084
Total assets	4,200		4,449
Liabilities
Other secured financings	691		684
Customer and other payables	25		9
Trading liabilities	36		10
Other liabilities	945		959
Total liabilities	1,697		1,662
Corporate Debt and Other Asset-Backed [Member]
Assets
Cash and cash equivalents	47
Total assets	47
Liabilities
Other secured financings	715
Total liabilities	715
Principal-Protected Notes [Member]
Assets
Trading assets	54		1
Total assets	54		1
Liabilities
Other secured financings	539		479
Trading liabilities	221
Unsecured short-term borrowings	44		48
Unsecured long-term borrowings	219		214
Total liabilities	1,023		741
Consolidated Variable Interest Entity, Total Carrying Amount [Member]
Assets
Cash and cash equivalents	255		112
Trading assets	57		27
Investments	846		835
Loans	2,077		2,392
Other assets	1,066		1,084
Total assets	4,301		4,450
Liabilities
Other secured financings	1,945		1,163
Customer and other payables	25		9
Trading liabilities	257		10
Unsecured short-term borrowings	44		48
Unsecured long-term borrowings	219		214
Other liabilities	945		959
Total liabilities	$ 3,435		$ 2,403