Fair value measurements - Financial assets and liabilities (Detail) - USD ($) $ in Millions		Mar. 31, 2024		Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		$ 17,167		$ 23,758
Investments in equity securities		335,864	[1]	353,842	[2]
Insurance and Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		17,167		23,758
Investments in equity securities		335,864		353,842
The Kraft Heinz Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments, fair value		12,009		12,035
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		4,503		10,269
Foreign governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		10,997		11,805
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,429		1,449
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		238		235
Fair Value, Measurements, Recurring [Member] | Quoted Prices (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities		325,182		343,358
Derivative contract assets	[3]	$ 38		$ 39
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other		Other
Derivative contract liabilities	[3]	$ 4		$ 7
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Accounts payable, accruals and other liabilities		Accounts payable, accruals and other liabilities
Fair Value, Measurements, Recurring [Member] | Quoted Prices (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		$ 28,128		$ 26,587
Fair Value, Measurements, Recurring [Member] | Quoted Prices (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		4,469		10,234
Fair Value, Measurements, Recurring [Member] | Quoted Prices (Level 1) [Member] | Foreign governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		10,748		11,559
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (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		898		892
Derivative contract assets	[3]	$ 183		$ 282
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other		Other
Derivative contract liabilities	[3]	$ 150		$ 111
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Accounts payable, accruals and other liabilities		Accounts payable, accruals and other liabilities
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (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		$ 36,668		$ 39,153
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (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		75,921		81,036
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (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		34		35
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		249		246
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		851		860
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		238		235
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities		10,672		10,474
Loans and finance receivables		24,083		23,298
Derivative contract assets	[3]	$ 17		$ 13
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other		Other
Derivative contract liabilities	[3]	$ 141		$ 95
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Accounts payable, accruals and other liabilities		Accounts payable, accruals and other liabilities
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (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		$ 25		$ 31
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		578		589
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		335,864		353,842
Loans and finance receivables		25,435		24,681
Derivative contract assets	[3]	$ 238		$ 334
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other		Other
Derivative contract liabilities	[3]	$ 295		$ 213
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Accounts payable, accruals and other liabilities		Accounts payable, accruals and other liabilities
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		$ 40,723		$ 42,692
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		82,031		85,579
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		29,147		28,640
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		4,503		10,269
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		10,997		11,805
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,429		1,449
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		238		235
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		335,864		353,842
Loans and finance receivables		24,981		24,190
Derivative contract assets	[3]	$ 238		$ 334
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other		Other
Derivative contract liabilities	[3]	$ 295		$ 213
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Accounts payable, accruals and other liabilities		Accounts payable, accruals and other liabilities
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		$ 36,693		$ 39,184
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		75,921		81,036
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		28,128		26,587
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		4,503		10,269
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		10,997		11,805
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,429		1,449
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		$ 238		$ 235

[1] Approximately 75% of the aggregate fair value was concentrated in five companies (American Express Company – $34.5 billion; Apple Inc. – $135.4 billion; Bank of America Corporation – $39.2 billion; The Coca-Cola Company – $24.5 billion and Chevron Corporation – $19.4 billion).

[2] Approximately 79% of the aggregate fair value was concentrated in five companies (American Express Company – $28.4 billion; Apple Inc. – $174.3 billion; Bank of America Corporation – $34.8 billion; The Coca-Cola Company – $23.6 billion and Chevron Corporation – $18.8 billion).

[3] Assets are included in other assets and liabilities are included in accounts payable, accruals and other liabilities.