Fair value measurements - Financial assets and liabilities (Detail) - USD ($) $ in Millions		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities		$ 122,032	[1]	$ 112,137	[2]
Investments in fixed maturity securities		23,465		26,027
Railroad, Utilities and Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - carrying value		59,085		57,739
Finance and Financial Products [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities		375		372
Investments in fixed maturity securities		33		39
Other investments		2,892		5,719
Loans and finance receivables - carrying value		13,300		12,772
Derivative contract liabilities		2,890		3,836
Notes payable and other borrowings - carrying value		15,384		11,951
Insurance and Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities		120,471		110,527
Investments in fixed maturity securities		23,432		25,988
Other investments		14,364		15,683
Notes payable and other borrowings - carrying value		27,175		14,599
Other Assets [Member] | Railroad, Utilities and Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities	[3]	1,186		1,238
Kraft Heinz (previously Heinz Holding) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Kraft Heinz common stock - carrying value		15,345		15,714
Investment in Kraft Heinz Preferred Stock - carrying value				7,710
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		4,527		3,427
States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,216		1,764
Foreign governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		9,001		11,468
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		7,604		7,926
Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,117		1,442
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		122,031		112,101
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				35
Loans and finance receivables - fair value		13		16
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		1		1
Other investments		17,256		21,402
Loans and finance receivables - fair value		13,704		13,096
Fair Value, Measurements, Recurring [Member] | Railroad, Utilities and Energy [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - fair value		65,774		62,471
Fair Value, Measurements, Recurring [Member] | Finance and Financial Products [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - fair value		15,469		11,887
Fair Value, Measurements, Recurring [Member] | Finance and Financial Products [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - fair value		356		476
Fair Value, Measurements, Recurring [Member] | Finance and Financial Products [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Index Put Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities		2,890		3,552
Fair Value, Measurements, Recurring [Member] | Finance and Financial Products [Member] | Significant Unobservable Inputs (Level 3) [Member] | Credit Default [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities				284
Fair Value, Measurements, Recurring [Member] | Insurance and Other [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - fair value		27,712		14,773
Fair Value, Measurements, Recurring [Member] | Other Assets [Member] | Quoted Prices (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract assets	[4]	5
Fair Value, Measurements, Recurring [Member] | Other Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract assets	[4]	43		5
Fair Value, Measurements, Recurring [Member] | Other Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract assets	[4]	94		98
Fair Value, Measurements, Recurring [Member] | Accounts Payable, Accruals and Other Liabilities [Member] | Railroad, Utilities and Energy [Member] | Quoted Prices (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities	[4]	3		13
Fair Value, Measurements, Recurring [Member] | Accounts Payable, Accruals and Other Liabilities [Member] | Railroad, Utilities and Energy [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities	[4]	114		177
Fair Value, Measurements, Recurring [Member] | Accounts Payable, Accruals and Other Liabilities [Member] | Railroad, Utilities and Energy [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities	[4]	28		47
Fair Value, Measurements, Recurring [Member] | Kraft Heinz (previously Heinz Holding) [Member] | Quoted Prices (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Kraft Heinz common stock - fair value		28,418		23,679
Fair Value, Measurements, Recurring [Member] | Kraft Heinz (previously Heinz Holding) [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Kraft Heinz Preferred Stock - fair value				8,363
Fair Value, Measurements, Recurring [Member] | U.S. Treasury, U.S. government corporations and agencies [Member] | Quoted Prices (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		3,099		2,485
Fair Value, Measurements, Recurring [Member] | U.S. Treasury, U.S. government corporations and agencies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,428		942
Fair Value, Measurements, Recurring [Member] | States, municipalities and political subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,216		1,764
Fair Value, Measurements, Recurring [Member] | Foreign governments [Member] | Quoted Prices (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		7,237		9,188
Fair Value, Measurements, Recurring [Member] | Foreign governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,764		2,280
Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		7,540		7,826
Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		64		100
Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,117		1,442
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		122,032		112,137
Other investments		17,256		21,402
Loans and finance receivables - carrying value		13,300		12,772
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 - carrying value		59,085		57,739
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Finance and Financial Products [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - carrying value		15,384		11,951
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Finance and Financial Products [Member] | Equity Index Put Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities		2,890		3,552
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Finance and Financial Products [Member] | Credit Default [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities				284
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 - carrying value		27,175		14,599
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract assets	[4]	142		103
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Accounts Payable, Accruals and Other Liabilities [Member] | Railroad, Utilities and Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities	[4]	145		237
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Kraft Heinz (previously Heinz Holding) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Kraft Heinz common stock - carrying value		15,345		15,714
Investment in Kraft Heinz Preferred Stock - carrying value				7,710
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		4,527		3,427
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,216		1,764
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		9,001		11,468
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		7,604		7,926
Fair Value, Measurements, Recurring [Member] | Carrying Value [Member] | Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,117		1,442
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		122,032		112,137
Other investments		17,256		21,402
Loans and finance receivables - fair value		13,717		13,112
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 - fair value		65,774		62,471
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Finance and Financial Products [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes payable and other borrowings - fair value		15,825		12,363
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Finance and Financial Products [Member] | Equity Index Put Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities		2,890		3,552
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Finance and Financial Products [Member] | Credit Default [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities				284
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 - fair value		27,712		14,773
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract assets	[4]	142		103
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Accounts Payable, Accruals and Other Liabilities [Member] | Railroad, Utilities and Energy [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative contract liabilities	[4]	145		237
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Kraft Heinz (previously Heinz Holding) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Kraft Heinz common stock - fair value		28,418		23,679
Investment in Kraft Heinz Preferred Stock - fair value				8,363
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		4,527		3,427
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		1,216		1,764
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		9,001		11,468
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		7,604		7,926
Fair Value, Measurements, Recurring [Member] | Fair Value [Member] | Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in fixed maturity securities		$ 1,117		$ 1,442

[1] Approximately 56% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company-$11.2 billion; Wells Fargo & Company-$27.6 billion; International Business Machines Corporation ("IBM")-$13.5 billion; and The Coca-Cola Company-$16.6 billion).

[2] Approximately 59% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company-$10.5 billion; Wells Fargo & Company-$27.2 billion; IBM-$11.2 billion; and The Coca-Cola Company-$17.2 billion).

[3] Included in other assets.

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