Investments in equity securities (Detail) - USD ($) $ in Millions	Sep. 30, 2023	[1]	Dec. 31, 2022	[2]
Summary of Investment Holdings [Line Items]
Cost Basis	$ 111,384		$ 131,610
Net Unrealized Gains	207,237		177,183
Fair Value	318,621		308,793
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	24,760		25,893
Net Unrealized Gains	37,202		43,663
Fair Value	61,962		69,556
Consumer Products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	35,471		40,508
Net Unrealized Gains	146,789		112,384
Fair Value	182,260		152,892
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	51,153		65,209
Net Unrealized Gains	23,246		21,136
Fair Value	$ 74,399		$ 86,345

[1] Approximately 78% of the aggregate fair value was concentrated in five companies (American Express Company – $22.6 billion; Apple Inc. – $156.8 billion; Bank of America Corporation – $28.3 billion; The Coca-Cola Company – $22.4 billion and Chevron Corporation – $18.6 billion).

[2] Approximately 75% of the aggregate fair value was concentrated in five companies (American Express Company – $22.4 billion; Apple Inc. – $119.0 billion; Bank of America Corporation – $34.2 billion; The Coca-Cola Company – $25.4 billion and Chevron Corporation – $30.0 billion).