Acquisitions (Details 2) (Customer relationship assets)	6 Months Ended
Jun. 30, 2011
Customer relationship assets
Acquired Finite-Lived Intangible Assets
Weighted average lives of finite-lived intangible assets associated with acquisitions (in years)	20

The calculated weighted-average amortization period of a major class of finite-lived intangible assets acquired during the current period either individually or as part of a group of assets (in either an asset acquisition or business combination). A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 44
-Subparagraph a(3)

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetWeightedAverageUsefulLife
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration