Fair value measurements - Financial Instruments (Detail) (USD $) In Millions	Jun. 30, 2011		Dec. 31, 2010
Fair Value Measurements [Line Items]
Investments in fixed maturity securities	$ 35,854		$ 34,883
Investments in equity securities	67,585		61,513
Insurance and Other [Member] | Carrying Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	10,161		12,471
Railroad, Utilities and Energy [Member] | Carrying Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	32,276		31,626
Derivative contract liabilities	464	[1]	621	[1]
Finance and Financial Products [Member] | Carrying Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	14,280		14,477
Derivative contract liabilities	8,086		8,371
Carrying Value [Member]
Fair Value Measurements [Line Items]
Other investments - carrying value	15,938		23,009
Investments in fixed maturity securities	35,854		34,883
Investments in equity securities	67,585		61,513
Loans and finance receivables	14,199		15,226
Derivative contract assets	519	[2]	574	[2]
Insurance and Other [Member] | Fair Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	10,424		12,705
Railroad, Utilities and Energy [Member] | Fair Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	34,619		33,932
Derivative contract liabilities	464	[1]	621	[1]
Finance and Financial Products [Member] | Fair Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	15,061		15,191
Derivative contract liabilities	8,086		8,371
Fair Value [Member]
Fair Value Measurements [Line Items]
Other investments - fair value	17,034		24,147
Investments in fixed maturity securities	35,854		34,883
Investments in equity securities	67,585		61,513
Loans and finance receivables	13,436		14,453
Derivative contract assets	519	[2]	574	[2]
Insurance and Other [Member]
Fair Value Measurements [Line Items]
Other investments - carrying value	13,121		19,333
Investments in fixed maturity securities	34,813		33,803
Investments in equity securities	66,364		59,819
Notes payable and other borrowings	10,161		12,471
Railroad, Utilities and Energy [Member]
Fair Value Measurements [Line Items]
Investments in equity securities	727	[3]	1,182	[3]
Notes payable and other borrowings	32,276		31,626
Finance and Financial Products [Member]
Fair Value Measurements [Line Items]
Other investments - carrying value	2,817		3,676
Investments in fixed maturity securities	1,041		1,080
Investments in equity securities	494	[3]	512	[3]
Loans and finance receivables	14,199		15,226
Notes payable and other borrowings	14,280		14,477
Derivative contract liabilities	$ 8,086		$ 8,371

[1] Included in Accounts payable, accruals and other liabilities

[2] Included in Other assets

[3] Included in Other assets.