Investments in equity securities (Detail) - USD ($) $ in Millions	Sep. 30, 2022	[1]	Dec. 31, 2021	[2]
Summary of Investment Holdings [Line Items]
Cost Basis	$ 142,310		$ 104,605
Net Unrealized Gains	163,857		246,114
Fair Value	306,167		350,719
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	32,148		26,822
Net Unrealized Gains	36,817		62,236
Fair Value	68,965		89,058
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	41,106		36,076
Net Unrealized Gains	116,615		154,945
Fair Value	157,721		191,021
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	69,056		41,707
Net Unrealized Gains	10,425		28,933
Fair Value	$ 79,481		$ 70,640

[1] Approximately 73% of the aggregate fair value was concentrated in five companies (American Express Company – $20.5 billion; Apple Inc. – $126.5 billion; Bank of America Corporation – $31.2 billion; The Coca-Cola Company – $22.4 billion and Chevron Corporation – $24.4 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).