Investments in equity securities (Detail) - USD ($) $ in Millions	Dec. 31, 2021		Dec. 31, 2020
Summary of Investment Holdings [Line Items]
Cost Basis	$ 104,605		$ 108,620
Net Unrealized Gains	246,114		172,550
Fair Value	350,719	[1]	281,170	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	26,822		26,312
Net Unrealized Gains	62,236		40,167
Fair Value	89,058		66,479
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	36,076		34,747
Net Unrealized Gains	154,945		111,583
Fair Value	191,021		146,330
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis	41,707		47,561
Net Unrealized Gains	28,933		20,800
Fair Value	$ 70,640		$ 68,361

[1] 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).

[2] Approximately 68% of the aggregate fair value was concentrated in four companies (American Express Company – $18.3 billion; Apple Inc. – $120.4 billion; Bank of America Corporation – $31.3 billion and The Coca-Cola Company – $21.9 billion).