Investments in equity securities (Detail) - USD ($) $ in Millions	Mar. 31, 2024	[1]	Dec. 31, 2023	[2]
Summary of Investment Holdings [Line Items]
Cost Basis	$ 103,753		$ 109,416
Net Unrealized Gains	232,111		244,426
Fair Value	335,864		353,842
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	28,513		27,136
Net Unrealized Gains	64,299		51,176
Fair Value	92,812		78,312
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	29,214		34,248
Net Unrealized Gains	134,364		166,895
Fair Value	163,578		201,143
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	46,026		48,032
Net Unrealized Gains	33,448		26,355
Fair Value	$ 79,474		$ 74,387

[1] Approximately 75% of the aggregate fair value was concentrated in five companies (American Express Company – $34.5 billion; Apple Inc. – $135.4 billion; Bank of America Corporation – $39.2 billion; The Coca-Cola Company – $24.5 billion and Chevron Corporation – $19.4 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).