Fair Value Measurements - Financial Assets Liabilities Summary (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial assets at fair value	$ 594,968	$ 535,036	$ 501,712
Total assets	$ 1,007,320	$ 944,903	$ 931,796
Total level 3 financial assets divided by total assets	2.30%	2.40%	2.40%
Total level 3 financial assets divided by total financial assets at fair value	3.90%	4.30%	4.40%
Total financial liabilities at fair value	$ 336,029	$ 290,368	$ 296,504
Total level 3 financial liabilities divided by total financial liabilities at fair value	7.70%	8.70%	8.00%
Counterparty and Cash Collateral Netting [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial assets at fair value	$ (67,550)	$ (56,747)	$ (49,383)
Total financial liabilities at fair value	(48,295)	(43,395)	(39,786)
Investments in funds at NAV [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial assets at fair value	4,232	4,086	3,936
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial assets at fair value	238,670	196,854	170,463
Total financial liabilities at fair value	59,545	56,715	54,151
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial assets at fair value	396,122	368,056	354,515
Total financial liabilities at fair value	299,001	251,854	258,335
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial assets at fair value	23,494	22,787	22,181
Total financial liabilities at fair value	$ 25,778	$ 25,194	$ 23,804