FVM - Fair value hierarchy - Liabilities (Detail) - USD ($) $ in Millions		Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[1]	$ 323,721	$ 361,707	$ 291,452
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	[1]	34,426	32,571	30,591
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	[1]	23,846	22,598	22,734
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	[1]	4,635	4,018	3,661
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	[1]	4,822	4,590	3,466
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]	1,096	1,349	698
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	[1]	152,280	206,649	120,880
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	[1]	54,899	93,217	54,013
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	[1]	49,894	50,674	36,571
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]	41,067	55,528	25,468
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	[1]	2,698	2,940	2,960
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	[1]	3,138	3,438	1,707
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	[1]	40,248	37,652	37,233
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	[1]	58,864	53,299	66,809
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	[1]	37,902	31,536	35,940
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	[1]	26,573	23,150	28,145
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	[1]	8,371	5,992	5,742
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]	2,852	2,297	2,022
Level 1
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[1]	29,087	28,211	26,176
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	[1]	28,216	26,965	25,791
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	[1]	23,464	22,289	22,526
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	[1]	38	22	40
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	[1]	4,052	3,880	2,820
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	[1]	662	774	404
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	[1]	871	1,246	385
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	[1]	447	636	248
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	[1]	7	6	7
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	[1]	0	4	3
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	[1]	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	[1]	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	[1]	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	[1]	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	[1]	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	[1]	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	[1]	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	[1]	0	0	0
Level 2
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[1]	280,337	321,207	252,518
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	[1]	6,093	5,463	4,726
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	[1]	306	282	149
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	[1]	4,558	3,921	3,606
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	[1]	770	710	646
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	[1]	431	532	294
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	[1]	148,116	201,770	118,498
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	[1]	54,385	92,515	53,705
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	[1]	49,048	49,776	36,434
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	[1]	39,622	53,968	24,171
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	[1]	1,781	1,875	2,448
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	[1]	3,128	3,437	1,707
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	[1]	40,248	37,652	37,233
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	[1]	49,123	46,013	56,943
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	[1]	36,757	30,309	35,119
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	[1]	26,573	23,150	28,145
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	[1]	8,371	5,992	5,742
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]	1,796	1,159	1,231
Level 3
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[1]	14,296	12,289	12,759
Level 3 | Equity instruments
Disclosure Of Fair Value Measurement Of Liabilities [Line Items]
Financial liabilities measured at fair value	[2]	100		100
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	[2]	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	[1]	117	143	75
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	[1]	76	26	59
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	[1]	39	74	16
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	[1]	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	[1]	2	43	0
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	[1]	3,293	3,633	1,996
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	[1]	67	65	60
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	[1]	838	892	130
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]	1,445	1,557	1,293
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	[1]	917	1,065	512
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	[1]	10	0	0
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	[1]	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	[1]	9,741	7,286	9,866
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	[1]	1,145	1,227	822
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	[1]	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	[1]	0	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	[1]	$ 1,057	$ 1,138	$ 791

[1] Bifurcated embedded derivatives are presented on the same balance sheet lines as their host contracts and are not included in this table. The fair value of these derivatives was not material for the periods presented

[2] The range of inputs is not disclosed as there is a dispersion of values given the diverse nature of the investments.