Derivatives and Hedging Activities - OTC Derivatives by Product Type and Tenor (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative Assets	$ 64,520	$ 45,252
Derivative Liabilities	56,698	43,802
OTC [Member]
Derivative [Line Items]
Derivative Assets	153,769	114,650
Derivative Liabilities	120,863	95,630
OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	103,748	78,098
Derivative Liabilities	66,211	49,237
OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	8,206	7,120
Derivative Liabilities	6,999	7,180
OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	26,198	21,544
Derivative Liabilities	24,532	23,428
OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	5,702	4,021
Derivative Liabilities	9,189	8,550
OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	20,833	13,135
Derivative Liabilities	24,850	16,503
OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(10,918)	(9,268)
Derivative Liabilities	(10,918)	(9,268)
OTC [Member] | Cross Tenor Counterparty Netting [Member]
Derivative [Line Items]
Derivative Assets	(20,089)	(15,639)
Derivative Liabilities	(20,089)	(15,639)
OTC [Member] | Cash Collateral Netting [Member]
Derivative [Line Items]
Cash collateral netting	(73,226)	(56,000)
Cash collateral netting	(52,125)	(42,144)
OTC [Member] | Counterparty and Cash Collateral Netting [Member]
Derivative [Line Items]
Derivative Assets	60,454	43,011
Derivative Liabilities	48,649	37,847
Less than 1 Year [Member] | OTC [Member]
Derivative [Line Items]
Derivative Assets	28,536	23,011
Derivative Liabilities	25,940	22,796
Less than 1 Year [Member] | OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	8,579	5,521
Derivative Liabilities	5,192	3,654
Less than 1 Year [Member] | OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	685	678
Derivative Liabilities	845	1,368
Less than 1 Year [Member] | OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	11,128	10,236
Derivative Liabilities	11,282	12,486
Less than 1 Year [Member] | OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	3,244	2,507
Derivative Liabilities	2,962	2,796
Less than 1 Year [Member] | OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	8,406	7,332
Derivative Liabilities	9,165	5,755
Less than 1 Year [Member] | OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(3,506)	(3,263)
Derivative Liabilities	(3,506)	(3,263)
1 - 5 Years [Member] | OTC [Member]
Derivative [Line Items]
Derivative Assets	38,987	25,553
Derivative Liabilities	33,498	25,729
1 - 5 Years [Member] | OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	21,362	15,183
Derivative Liabilities	12,242	9,113
1 - 5 Years [Member] | OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	3,532	3,259
Derivative Liabilities	3,577	4,052
1 - 5 Years [Member] | OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	6,001	5,063
Derivative Liabilities	7,237	6,906
1 - 5 Years [Member] | OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	1,916	1,212
Derivative Liabilities	1,862	1,950
1 - 5 Years [Member] | OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	10,223	4,509
Derivative Liabilities	12,627	7,381
1 - 5 Years [Member] | OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(4,047)	(3,673)
Derivative Liabilities	(4,047)	(3,673)
Greater than 5 Years [Member] | OTC [Member]
Derivative [Line Items]
Derivative Assets	86,246	66,086
Derivative Liabilities	61,425	47,105
Greater than 5 Years [Member] | OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	73,807	57,394
Derivative Liabilities	48,777	36,470
Greater than 5 Years [Member] | OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	3,989	3,183
Derivative Liabilities	2,577	1,760
Greater than 5 Years [Member] | OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	9,069	6,245
Derivative Liabilities	6,013	4,036
Greater than 5 Years [Member] | OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	542	302
Derivative Liabilities	4,365	3,804
Greater than 5 Years [Member] | OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	2,204	1,294
Derivative Liabilities	3,058	3,367
Greater than 5 Years [Member] | OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(3,365)	(2,332)
Derivative Liabilities	$ (3,365)	$ (2,332)