Other investments (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Insurance and Other [Member] | Fixed Maturity and Equity Securities [Member]
Other Investments [Line Items]
Cost	$ 15,817	$ 15,700
Net Unrealized Gains	1,841	4,758
Fair Value	17,658	20,458
Carrying Value	16,633	19,333
Finance and Financial Products [Member] | Fixed Maturity and Equity Securities [Member]
Other Investments [Line Items]
Cost	3,198	2,742
Net Unrealized Gains	699	947
Fair Value	3,897	3,689
Carrying Value	3,886	3,676
Fixed Maturity and Equity Securities [Member]
Other Investments [Line Items]
Cost	19,015	18,442
Net Unrealized Gains	2,540	5,705
Fair Value	21,555	24,147
Carrying Value	20,519	23,009
Insurance and Other [Member]
Other Investments [Line Items]
Carrying Value	16,633	19,333
Finance and Financial Products [Member]
Other Investments [Line Items]
Carrying Value	$ 3,886	$ 3,676