v3.26.1
Investments in equity securities (Detail) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Summary of Investment Holdings [Line Items]    
Cost Basis $ 84,595 $ 85,389
Net Unrealized Gains 203,439 212,389
Fair Value 288,034 297,778
Banks, insurance and finance [Member]    
Summary of Investment Holdings [Line Items]    
Cost Basis 14,685 15,454
Net Unrealized Gains 69,891 88,675
Fair Value 84,576 104,129
Consumer products [Member]    
Summary of Investment Holdings [Line Items]    
Cost Basis 8,847 11,899
Net Unrealized Gains 82,191 83,055
Fair Value 91,038 94,954
Commercial, industrial and other [Member]    
Summary of Investment Holdings [Line Items]    
Cost Basis 61,063 58,036
Net Unrealized Gains 51,357 40,659
Fair Value $ 112,420 $ 98,695