v3.26.1
Fair value measurements - Financial assets and liabilities (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities $ 17,034 $ 17,816
Investments in equity securities 323,779 297,778
Insurance and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 17,034 17,816
Investments in equity securities 323,779 297,778
Other assets 27,813 24,413
Railroad, Utilities and Energy [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets 25,169 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 3,002 3,849
Foreign governments [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 12,668 12,542
Corporate and Other [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments in fixed maturity securities 1,364 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 314,025 288,232
Other assets 10 13
Other liabilities 13 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 20,560 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 2,969 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 12,580 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 279 294
Other assets 142 119
Other liabilities 496 119
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 38,079 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 78,225 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 88 131
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 947 983
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 9,744 9,536
Loans and finance receivables 30,070 30,238
Other assets 16 9
Other liabilities 68 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 417 442
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 323,779 297,778
Loans and finance receivables 30,724 29,836
Other assets 168 141
Other liabilities 577 188
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 43,302 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 85,297 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 19,487 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 3,002 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 12,668 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 1,364 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 323,779 297,778
Loans and finance receivables 30,349 30,532
Other assets 168 141
Other liabilities 577 188
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 38,102 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 78,225 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 20,560 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 3,002 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 12,668 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 $ 1,364 $ 1,425