Other investments (Detail) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Insurance and Other [Member] | Fixed Maturity and Equity Securities [Member]
Other Investments [Line Items]
Cost	$ 11,809	$ 15,700
Unrealized Gains	2,396	4,758
Fair Value	14,205	20,458
Carrying Value	13,121	19,333
Finance and Financial Products [Member] | Fixed Maturity and Equity Securities [Member]
Other Investments [Line Items]
Cost	2,198	2,742
Unrealized Gains	631	947
Fair Value	2,829	3,689
Carrying Value	2,817	3,676
Fixed Maturity and Equity Securities [Member]
Other Investments [Line Items]
Cost	14,007	18,442
Unrealized Gains	3,027	5,705
Fair Value	17,034	24,147
Carrying Value	15,938	23,009
Insurance and Other [Member]
Other Investments [Line Items]
Carrying Value	13,121	19,333
Finance and Financial Products [Member]
Other Investments [Line Items]
Carrying Value	$ 2,817	$ 3,676