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Acquisitions Of Businesses (Details) $ in Thousands | Nov. 01, 2017 Company | Mar. 01, 2017 USD ($) Company | Jan. 04, 2017 Company | Mar. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
--- | --- | --- | --- | --- | ---
Business Acquisition [Line Items] |  |  |  |  |
Goodwill |  |  |  | $ 965,046 | $ 964,893
Number of businesses acquired | Company | 1 | 1 | 1 |  |
2017 Acquisitions [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Purchase price |  | $ 109,300 |  |  |
Working capital acquired |  | 9,600 |  |  |
Other net assets |  | 2,300 |  |  |
Goodwill |  | 40,800 |  |  |
Identifiable intangible assets |  | $ 56,600 |  |  |

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- Definition Amount of intangible assets, excluding goodwill, acquired at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472 + Details
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 + Details
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