Goodwill and other intangible assets - Intangible assets - Narrative (Detail) (USD $) In Millions	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Finite Lived and Indefinite Lived Intangible Assets [Line Items]
Amortization expense	$ 565	$ 521
Intangible assets with indefinite lives	$ 2,040		$ 1,635

Aggregate amount of intangible asset amortization recognized as expense during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 45

-Subparagraph a(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=6905858&loc=d3e16323-109275

Name:	us-gaap_FiniteLivedIntangibleAssetsAmortizationExpense
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration