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Business Combinations - Acquisition Method for Recording Business Combinations (Parenthetical) (Detail) | 3 Months Ended
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Mar. 31, 2017
Construction Risk Solutions, LLC [Member] |
Business Acquisition [Line Items] |
Effective Date of Acquisition | Jan. 01, 2017
Hill, Chesson And Woody [Member] |
Business Acquisition [Line Items] |
Effective Date of Acquisition | Jan. 01, 2017
Presidio Group, Inc. [Member] |
Business Acquisition [Line Items] |
Effective Date of Acquisition | Jan. 01, 2017
Nine Other Acquisitions [Member] |
Business Acquisition [Line Items] |
Effective Year of Acquisition | 2017

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- Definition Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e845-128460 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Acquisition Date -URI http://asc.fasb.org/extlink&oid=6919109 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e848-128460 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463 + Details
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