Derivatives and Hedging Activities - Fair Value of Derivatives by Level (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Total financial assets at fair value	$ 614,112	$ 539,568
Total financial liabilities at fair value	(350,706)	(332,959)
Fair value included in financial instruments	(136,358)	(108,835)
Level 1 [Member]
Derivative [Line Items]
Total financial assets at fair value	217,934	242,562
Total financial liabilities at fair value	(63,117)	(54,790)
Level 2 [Member]
Derivative [Line Items]
Total financial assets at fair value	440,469	325,259
Total financial liabilities at fair value	(320,820)	(293,902)
Level 3 [Member]
Derivative [Line Items]
Total financial assets at fair value	30,776	23,068
Total financial liabilities at fair value	(27,565)	(25,938)
Derivatives [Member]
Derivative [Line Items]
Total financial assets at fair value	153,183	100,779
Total financial liabilities at fair value	(122,835)	(85,473)
Fair value included in financial instruments	74,571	45,252
Fair value included in financial instruments	(62,039)	(43,802)
Derivatives [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	373,956	280,003
Total financial liabilities at fair value	(339,504)	(251,521)
Derivatives [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	24,152	20,729
Total financial liabilities at fair value	(22,374)	(20,789)
Derivatives [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	132,067	80,365
Total financial liabilities at fair value	(131,471)	(82,224)
Derivatives [Member] | Commodity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	25,532	11,138
Total financial liabilities at fair value	(30,156)	(15,549)
Derivatives [Member] | Equity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	87,549	49,661
Total financial liabilities at fair value	(89,403)	(56,507)
Derivatives [Member] | Gross Fair Value Of Derivative [Member]
Derivative [Line Items]
Total financial assets at fair value	643,256	441,896
Total financial liabilities at fair value	(612,908)	(426,590)
Derivatives [Member] | Counterparty Netting in Levels [Member]
Derivative [Line Items]
Total financial assets at fair value	(490,073)	(341,117)
Total financial liabilities at fair value	490,073	341,117
Derivatives [Member] | Cross Level Counterparty Netting Adjustment [Member]
Derivative [Line Items]
Total financial assets at fair value	(813)	473
Total financial liabilities at fair value	813	(473)
Derivatives [Member] | Cash Collateral Netting [Member]
Derivative [Line Items]
Cash collateral netting	(77,799)	(56,000)
Cash collateral netting	59,983	42,144
Derivatives [Member] | Level 1 [Member]
Derivative [Line Items]
Total financial assets at fair value	31	24
Total financial liabilities at fair value	(49)	(29)
Derivatives [Member] | Level 1 [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	18	3
Total financial liabilities at fair value	(32)	(3)
Derivatives [Member] | Level 1 [Member] | Equity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	13	21
Total financial liabilities at fair value	(17)	(26)
Derivatives [Member] | Level 1 [Member] | Gross Fair Value Of Derivative [Member]
Derivative [Line Items]
Total financial assets at fair value	31	24
Total financial liabilities at fair value	(49)	(29)
Derivatives [Member] | Level 2 [Member]
Derivative [Line Items]
Total financial assets at fair value	145,771	96,101
Total financial liabilities at fair value	(117,065)	(80,815)
Derivatives [Member] | Level 2 [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	373,085	279,443
Total financial liabilities at fair value	(338,885)	(251,050)
Derivatives [Member] | Level 2 [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	19,560	17,204
Total financial liabilities at fair value	(20,300)	(19,141)
Derivatives [Member] | Level 2 [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	131,624	80,178
Total financial liabilities at fair value	(131,089)	(81,826)
Derivatives [Member] | Level 2 [Member] | Commodity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	24,784	10,648
Total financial liabilities at fair value	(29,796)	(15,306)
Derivatives [Member] | Level 2 [Member] | Equity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	85,247	48,953
Total financial liabilities at fair value	(85,524)	(53,817)
Derivatives [Member] | Level 2 [Member] | Gross Fair Value Of Derivative [Member]
Derivative [Line Items]
Total financial assets at fair value	634,300	436,426
Total financial liabilities at fair value	(605,594)	(421,140)
Derivatives [Member] | Level 2 [Member] | Counterparty Netting in Levels [Member]
Derivative [Line Items]
Total financial assets at fair value	(488,529)	(340,325)
Total financial liabilities at fair value	488,529	340,325
Derivatives [Member] | Level 3 [Member]
Derivative [Line Items]
Total financial assets at fair value	7,381	4,654
Total financial liabilities at fair value	(5,721)	(4,629)
Derivatives [Member] | Level 3 [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	853	557
Total financial liabilities at fair value	(587)	(468)
Derivatives [Member] | Level 3 [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	4,592	3,525
Total financial liabilities at fair value	(2,074)	(1,648)
Derivatives [Member] | Level 3 [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	443	187
Total financial liabilities at fair value	(382)	(398)
Derivatives [Member] | Level 3 [Member] | Commodity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	748	490
Total financial liabilities at fair value	(360)	(243)
Derivatives [Member] | Level 3 [Member] | Equity Contract [Member]
Derivative [Line Items]
Total financial assets at fair value	2,289	687
Total financial liabilities at fair value	(3,862)	(2,664)
Derivatives [Member] | Level 3 [Member] | Gross Fair Value Of Derivative [Member]
Derivative [Line Items]
Total financial assets at fair value	8,925	5,446
Total financial liabilities at fair value	(7,265)	(5,421)
Derivatives [Member] | Level 3 [Member] | Counterparty Netting in Levels [Member]
Derivative [Line Items]
Total financial assets at fair value	(1,544)	(792)
Total financial liabilities at fair value	$ 1,544	$ 792