Investments in equity securities (Detail) - USD ($) $ in Millions	Mar. 31, 2022		Dec. 31, 2021
Summary of Investment Holdings [Line Items]
Cost Basis	$ 145,536		$ 104,605
Net Unrealized Gains	245,002		246,114
Fair Value	390,538	[1]	350,719	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	36,472		26,822
Net Unrealized Gains	61,657		62,236
Fair Value	98,129		89,058
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	40,932		36,076
Net Unrealized Gains	153,536		154,945
Fair Value	194,468		191,021
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	68,132		41,707
Net Unrealized Gains	29,809		28,933
Fair Value	$ 97,941		$ 70,640

[1] Approximately 66% of the aggregate fair value was concentrated in four companies (American Express Company – $28.4 billion; Apple Inc. – $159.1 billion; Bank of America Corporation – $42.6 billion and Chevron Corporation – $25.9 billion).

[2] Approximately 73% of the aggregate fair value was concentrated in four companies (American Express Company – $24.8 billion; Apple Inc. – $161.2 billion; Bank of America Corporation – $46.0 billion and The Coca-Cola Company – $23.7 billion).