Investments in equity securities (Detail) - USD ($) $ in Millions	Sep. 30, 2024	[1]	Dec. 31, 2023	[2]
Summary of Investment Holdings [Line Items]
Cost Basis	$ 78,112		$ 109,416
Net Unrealized Gains	193,538		244,426
Fair Value	271,650		353,842
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	21,165		27,136
Net Unrealized Gains	71,383		51,176
Fair Value	92,548		78,312
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	11,341		34,248
Net Unrealized Gains	90,651		166,895
Fair Value	101,992		201,143
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	45,606		48,032
Net Unrealized Gains	31,504		26,355
Fair Value	$ 77,110		$ 74,387

[1] Approximately 70% of the aggregate fair value was concentrated in five companies (American Express Company – $41.1 billion; Apple Inc. – $69.9 billion; Bank of America Corporation – $31.7 billion; The Coca-Cola Company – $28.7 billion and Chevron Corporation – $17.5 billion).

[2] Approximately 79% of the aggregate fair value was concentrated in five companies (American Express Company – $28.4 billion; Apple Inc. – $174.3 billion; Bank of America Corporation – $34.8 billion; The Coca-Cola Company – $23.6 billion and Chevron Corporation – $18.8 billion).