Fair value measurements - Financial Instruments (Detail) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Fair Value Measurements [Line Items]
Investments in fixed maturity securities	$ 34,048		$ 34,883
Investments in equity securities	68,062		61,513
Insurance and Other [Member] | Carrying Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	13,748		12,471
Railroad, Utilities and Energy [Member] | Carrying Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	32,644		31,626
Derivative contract liabilities	492	[1]	621	[1]
Finance and Financial Products [Member] | Carrying Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	14,092		14,477
Derivative contract liabilities	10,421		8,371
Carrying Value [Member]
Fair Value Measurements [Line Items]
Investments in fixed maturity securities	34,048		34,883
Investments in equity securities	68,062		61,513
Loans and finance receivables	14,003		15,226
Derivative contract assets	278	[2]	574	[2]
Other investments - carrying value	20,519		23,009
Insurance and Other [Member] | Fair Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	14,200		12,705
Railroad, Utilities and Energy [Member] | Fair Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	37,289		33,932
Derivative contract liabilities	492	[1]	621	[1]
Finance and Financial Products [Member] | Fair Value [Member]
Fair Value Measurements [Line Items]
Notes payable and other borrowings	14,934		15,191
Derivative contract liabilities	10,421		8,371
Fair Value [Member]
Fair Value Measurements [Line Items]
Investments in fixed maturity securities	34,048		34,883
Investments in equity securities	68,062		61,513
Loans and finance receivables	13,335		14,453
Derivative contract assets	278	[2]	574	[2]
Other investments - fair value	21,555		24,147
Insurance and Other [Member]
Fair Value Measurements [Line Items]
Investments in fixed maturity securities	33,031		33,803
Investments in equity securities	67,225		59,819
Other investments - carrying value	16,633		19,333
Notes payable and other borrowings	13,748		12,471
Railroad, Utilities and Energy [Member]
Fair Value Measurements [Line Items]
Investments in equity securities	381	[3]	1,182	[3]
Notes payable and other borrowings	32,644		31,626
Finance and Financial Products [Member]
Fair Value Measurements [Line Items]
Investments in fixed maturity securities	1,017		1,080
Investments in equity securities	456	[3]	512	[3]
Loans and finance receivables	14,003		15,226
Other investments - carrying value	3,886		3,676
Notes payable and other borrowings	14,092		14,477
Derivative contract liabilities	$ 10,421		$ 8,371

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

[2] Included in Other assets

[3] Included in Other assets.