Derivatives and Hedging Activities - OTC Derivatives by Product Type and Tenor (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Assets	$ 49,872	$ 44,846
Derivative Liabilities	45,721	42,594
OTC [Member]
Derivative [Line Items]
Derivative Assets	131,496	102,443
Derivative Liabilities	107,210	91,814
OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	92,488	63,413
Derivative Liabilities	63,655	42,723
OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	7,915	7,847
Derivative Liabilities	7,629	6,712
OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	26,983	22,538
Derivative Liabilities	24,415	24,898
OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	4,249	7,224
Derivative Liabilities	8,038	10,079
OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	10,627	11,535
Derivative Liabilities	14,239	17,516
OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(10,766)	(10,114)
Derivative Liabilities	(10,766)	(10,114)
OTC [Member] | Cross Tenor Counterparty Netting [Member]
Derivative [Line Items]
Derivative Assets	(17,958)	(13,143)
Derivative Liabilities	(17,958)	(13,143)
OTC [Member] | Cash Collateral Netting [Member]
Derivative [Line Items]
Cash collateral netting	(66,722)	(48,724)
Cash collateral netting	(47,467)	(39,127)
OTC [Member] | Counterparty and Cash Collateral Netting [Member]
Derivative [Line Items]
Derivative Assets	46,816	40,576
Derivative Liabilities	41,785	39,544
Less than 1 Year [Member] | OTC [Member]
Derivative [Line Items]
Derivative Assets	24,228	21,124
Derivative Liabilities	23,557	29,013
Less than 1 Year [Member] | OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	5,328	2,810
Derivative Liabilities	6,351	4,193
Less than 1 Year [Member] | OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	587	807
Derivative Liabilities	1,222	1,127
Less than 1 Year [Member] | OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	14,036	10,976
Derivative Liabilities	11,118	13,553
Less than 1 Year [Member] | OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	2,835	4,978
Derivative Liabilities	2,388	4,271
Less than 1 Year [Member] | OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	4,572	4,962
Derivative Liabilities	5,608	9,278
Less than 1 Year [Member] | OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(3,130)	(3,409)
Derivative Liabilities	(3,130)	(3,409)
1 - 5 Years [Member] | OTC [Member]
Derivative [Line Items]
Derivative Assets	29,363	25,391
Derivative Liabilities	26,817	24,155
1 - 5 Years [Member] | OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	18,864	13,177
Derivative Liabilities	10,728	9,153
1 - 5 Years [Member] | OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	3,380	3,676
Derivative Liabilities	4,178	4,173
1 - 5 Years [Member] | OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	5,691	5,076
Derivative Liabilities	8,386	6,871
1 - 5 Years [Member] | OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	1,056	2,101
Derivative Liabilities	2,192	2,663
1 - 5 Years [Member] | OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	4,836	5,244
Derivative Liabilities	5,797	5,178
1 - 5 Years [Member] | OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(4,464)	(3,883)
Derivative Liabilities	(4,464)	(3,883)
Greater than 5 Years [Member] | OTC [Member]
Derivative [Line Items]
Derivative Assets	77,905	55,928
Derivative Liabilities	56,836	38,646
Greater than 5 Years [Member] | OTC [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Assets	68,296	47,426
Derivative Liabilities	46,576	29,377
Greater than 5 Years [Member] | OTC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Derivative Assets	3,948	3,364
Derivative Liabilities	2,229	1,412
Greater than 5 Years [Member] | OTC [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Assets	7,256	6,486
Derivative Liabilities	4,911	4,474
Greater than 5 Years [Member] | OTC [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Assets	358	145
Derivative Liabilities	3,458	3,145
Greater than 5 Years [Member] | OTC [Member] | Equity Contract [Member]
Derivative [Line Items]
Derivative Assets	1,219	1,329
Derivative Liabilities	2,834	3,060
Greater than 5 Years [Member] | OTC [Member] | Counterparty Netting in Tenors [Member]
Derivative [Line Items]
Derivative Assets	(3,172)	(2,822)
Derivative Liabilities	$ (3,172)	$ (2,822)