v3.26.1
Fair value measurements - Financial assets and liabilities (Detail) - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities $ 17,669 $ 17,816
Investments in equity securities 288,034 297,778
Insurance and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 17,669 17,816
Investments in equity securities 288,034 297,778
Other assets 27,412 24,413
Railroad, Utilities and Energy [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets 22,917 20,941
U.S. Treasury, U.S. government corporations and agencies [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 3,880 3,849
Foreign governments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 12,391 12,542
Corporate and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 1,398 1,425
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in equity securities 277,285 288,232
Other assets 13 13
Other liabilities 15 13
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | The Kraft Heinz Company and Occidental Petroleum Corporation [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity method investments, fair value 24,545 18,791
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury, U.S. government corporations and agencies [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 3,847 3,815
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign governments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 12,268 12,411
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in equity securities 10 10
Loans and finance receivables 223 294
Other assets 168 119
Other liabilities 281 119
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Insurance and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 37,418 40,892
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Railroad, Utilities and Energy [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 78,118 76,803
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury, U.S. government corporations and agencies [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 33 34
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign governments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 123 131
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 964 983
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in equity securities 10,739 9,536
Loans and finance receivables 29,432 30,238
Other assets 12 9
Other liabilities 69 56
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Insurance and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 23 32
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 434 442
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in equity securities 288,034 297,778
Loans and finance receivables 30,101 29,836
Other assets 193 141
Other liabilities 365 188
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Insurance and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 42,835 45,763
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Railroad, Utilities and Energy [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 86,051 83,318
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | The Kraft Heinz Company and Occidental Petroleum Corporation [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity method investments, fair value 19,497 19,528
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | U.S. Treasury, U.S. government corporations and agencies [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 3,880 3,849
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Foreign governments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 12,391 12,542
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Corporate and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 1,398 1,425
Fair Value, Measurements, Recurring [Member] | Fair Value [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in equity securities 288,034 297,778
Loans and finance receivables 29,655 30,532
Other assets 193 141
Other liabilities 365 188
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Insurance and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 37,441 40,924
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Railroad, Utilities and Energy [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notes payable and other borrowings 78,118 76,803
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | The Kraft Heinz Company and Occidental Petroleum Corporation [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity method investments, fair value 24,545 18,791
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | U.S. Treasury, U.S. government corporations and agencies [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 3,880 3,849
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Foreign governments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 12,391 12,542
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Corporate and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities $ 1,398 $ 1,425