v3.25.2
Investments in equity securities - Narrative (Detail)
$ / shares in Units, $ in Billions
 6 Months Ended 12 Months Ended
Jun. 30, 2025
USD ($)
Company
$ / shares
shares
Dec. 31, 2024
Company
Summary of Investment Holdings [Line Items]    
Investment, Type [Extensible Enumeration] us-gaap:USTreasuryBillSecuritiesMember us-gaap:USTreasuryBillSecuritiesMember
American Express Company [Member]    
Summary of Investment Holdings [Line Items]    
Investment owned, common shares outstanding | shares 151,600,000  
Investment owned, percent of common shares outstanding 21.80%  
Equity Securities [Member] | Investment Concentration [Member] | American Express Company, Apple Inc., Bank of America Corporation, The Coca-Cola Company and Chevron Corporation [Member]    
Summary of Investment Holdings [Line Items]    
Number of holdings in concentration percentage | Company 5 5
Concentration percentage 67.00% 71.00%
Occidental Petroleum Corporation [Member] | Investment Commitment [Member]    
Summary of Investment Holdings [Line Items]    
Investment in preferred stock, liquidation value | $ $ 8.5  
Number of common shares that can be purchased | shares 83,900,000  
Exercise price for warrants, per share | $ / shares $ 59.59  
Investment in preferred stock, stated dividend rate 8.00%  
Investment, Type [Extensible Enumeration] Cumulative Perpetual Preferred Stock [Member]  
Investment in preferred stock, redemption year start 2029  
Investment in preferred stock, redemption price percentage of liquidation value 105.00%  
Liquidation value of mandatory redemption notifications | $ $ 1.5  
Warrants exercisable period after the date preferred stock is fully redeemed 1 year