FVM - Fair value hierarchy - Liabilities (Detail) - USD ($) $ in Millions		Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		$ 299,869	$ 324,088	$ 325,069
Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		33,348	37,062	33,595
Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Equity instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		21,288	26,392	22,985
Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Corporate and municipal bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		4,642	4,757	4,089
Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Government bills / bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		6,347	4,975	4,678
Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Investment fund units
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		1,028	891	1,828
Measured at fair value on a recurring basis | Derivative financial instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		121,686	146,036	161,102
Measured at fair value on a recurring basis | Derivative financial instruments | Foreign exchange contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		47,387	67,638	70,527
Measured at fair value on a recurring basis | Derivative financial instruments | Interest rate contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		32,703	34,046	43,916
Measured at fair value on a recurring basis | Derivative financial instruments | Equity / index contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		36,342	38,684	41,176
Measured at fair value on a recurring basis | Derivative financial instruments | Credit derivative contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		2,392	2,508	2,931
Measured at fair value on a recurring basis | Derivative financial instruments | Commodity contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		2,085	1,966	2,027
Measured at fair value on a recurring basis | Brokerage payables designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		39,129	45,600	38,742
Measured at fair value on a recurring basis | Debt issued designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		75,065	66,535	61,243
Measured at fair value on a recurring basis | Other financial liabilities designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		30,642	28,855	30,387
Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Financial liabilities related to unit-linked investment contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		22,217	21,357	20,975
Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Securities financing transactions
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		6,184	5,651	7,317
Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Over-the-counter debt instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		2,142	1,787	2,060
Level 1
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		27,791	32,291	27,635
Level 1 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		27,038	30,887	26,888
Level 1 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Equity instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		20,826	26,190	22,519
Level 1 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Corporate and municipal bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		37	32	31
Level 1 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Government bills / bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		5,727	4,168	3,642
Level 1 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Investment fund units
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		442	492	696
Level 1 | Measured at fair value on a recurring basis | Derivative financial instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		754	1,404	746
Level 1 | Measured at fair value on a recurring basis | Derivative financial instruments | Foreign exchange contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		280	541	316
Level 1 | Measured at fair value on a recurring basis | Derivative financial instruments | Interest rate contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Derivative financial instruments | Equity / index contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		9	0	0
Level 1 | Measured at fair value on a recurring basis | Derivative financial instruments | Credit derivative contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Derivative financial instruments | Commodity contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Brokerage payables designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Debt issued designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Financial liabilities related to unit-linked investment contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Securities financing transactions
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 1 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Over-the-counter debt instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 2
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		253,679	275,442	282,222
Level 2 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		6,216	6,114	6,652
Level 2 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Equity instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		387	151	425
Level 2 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Corporate and municipal bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		4,592	4,718	4,048
Level 2 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Government bills / bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		620	807	1,036
Level 2 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Investment fund units
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		581	397	1,127
Level 2 | Measured at fair value on a recurring basis | Derivative financial instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		117,983	141,518	156,884
Level 2 | Measured at fair value on a recurring basis | Derivative financial instruments | Foreign exchange contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		47,048	67,043	70,149
Level 2 | Measured at fair value on a recurring basis | Derivative financial instruments | Interest rate contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		32,177	33,501	43,389
Level 2 | Measured at fair value on a recurring basis | Derivative financial instruments | Equity / index contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		34,431	36,614	38,870
Level 2 | Measured at fair value on a recurring basis | Derivative financial instruments | Credit derivative contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		2,000	2,139	2,403
Level 2 | Measured at fair value on a recurring basis | Derivative financial instruments | Commodity contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		2,034	1,907	2,003
Level 2 | Measured at fair value on a recurring basis | Brokerage payables designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		39,129	45,600	38,742
Level 2 | Measured at fair value on a recurring basis | Debt issued designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		60,321	53,900	50,273
Level 2 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		30,032	28,310	29,671
Level 2 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Financial liabilities related to unit-linked investment contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		22,217	21,357	20,975
Level 2 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Securities financing transactions
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		6,181	5,651	7,317
Level 2 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Over-the-counter debt instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		1,550	1,261	1,363
Level 3
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		18,398	16,355	15,212
Level 3 | Equity instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[1]	100		0
Level 3 | Corporate and municipal bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0		0
Level 3 | Investment fund units
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[1]	0		0
Level 3 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		94	61	55
Level 3 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Equity instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		75	50	40
Level 3 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Corporate and municipal bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		13	7	9
Level 3 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Government bills / bonds
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 3 | Measured at fair value on a recurring basis | Financial liabilities at fair value held for trading | Investment fund units
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		6	3	5
Level 3 | Measured at fair value on a recurring basis | Derivative financial instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		2,950	3,114	3,471
Level 3 | Measured at fair value on a recurring basis | Derivative financial instruments | Foreign exchange contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		59	54	61
Level 3 | Measured at fair value on a recurring basis | Derivative financial instruments | Interest rate contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		526	546	527
Level 3 | Measured at fair value on a recurring basis | Derivative financial instruments | Equity / index contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		1,902	2,070	2,306
Level 3 | Measured at fair value on a recurring basis | Derivative financial instruments | Credit derivative contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		392	369	528
Level 3 | Measured at fair value on a recurring basis | Derivative financial instruments | Commodity contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		51	59	24
Level 3 | Measured at fair value on a recurring basis | Brokerage payables designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 3 | Measured at fair value on a recurring basis | Debt issued designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		14,744	12,635	10,970
Level 3 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		610	545	716
Level 3 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Financial liabilities related to unit-linked investment contracts
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		0	0	0
Level 3 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Securities financing transactions
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		3	0	0
Level 3 | Measured at fair value on a recurring basis | Other financial liabilities designated at fair value | Over-the-counter debt instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value		$ 592	$ 526	$ 697

[1] <div>The range of inputs is not disclosed, as there is a dispersion of values given the diverse nature of the investments.</div>