Goodwill and other intangible assets (Detail) (USD $) In Millions	9 Months Ended	12 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Goodwill [Line Items]
Balance at beginning of year	$ 49,006	$ 33,972
Acquisition of businesses	4,325	15,069
Other	(21)	(35)
Balance at end of period	$ 53,310	$ 49,006

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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