v3.26.1
Investments in equity securities (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Summary of Investment Holdings [Line Items]    
Cost Basis $ 106,521 $ 85,389
Net Unrealized Gains 217,258 212,389
Fair Value 323,779 297,778
Banks, insurance and finance [Member]    
Summary of Investment Holdings [Line Items]    
Cost Basis 15,729 15,454
Net Unrealized Gains 78,748 88,675
Fair Value 94,477 104,129
Consumer products [Member]    
Summary of Investment Holdings [Line Items]    
Cost Basis 8,650 11,899
Net Unrealized Gains 91,836 83,055
Fair Value 100,486 94,954
Commercial, industrial and other [Member]    
Summary of Investment Holdings [Line Items]    
Cost Basis 82,142 58,036
Net Unrealized Gains 46,674 40,659
Fair Value $ 128,816 $ 98,695