Acquisitions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013 acquisition	Dec. 31, 2012 acquisition	Dec. 31, 2011 acquisition
Summarized information related to acquisitions
Number of acquisitions	9	23	28
Net cash paid during the year	$ 369	$ 723	$ 1,308

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration