Investments in equity securities (Detail) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Investments in equity securities [Line Items]
Cost Basis	$ 39,505	$ 35,544
Unrealized Gains	28,771	26,641
Unrealized Losses	(691)	(672)
Fair Value	67,585	61,513
Equity Securities [Member] | Banks, insurance and finance [Member]
Investments in equity securities [Line Items]
Cost Basis	15,562	15,519
Unrealized Gains	10,334	9,549
Unrealized Losses	(688)	(454)
Fair Value	25,208	24,614
Equity Securities [Member] | Consumer products [Member]
Investments in equity securities [Line Items]
Cost Basis	13,227	13,551
Unrealized Gains	13,607	12,410
Unrealized Losses		(212)
Fair Value	26,834	25,749
Equity Securities [Member] | Commercial, industrial and other [Member]
Investments in equity securities [Line Items]
Cost Basis	10,716	6,474
Unrealized Gains	4,830	4,682
Unrealized Losses	(3)	(6)
Fair Value	$ 15,543	$ 11,150