Goodwill - Schedule of Changes in Carrying Amount of Goodwill (Details) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Goodwill [Line Items]
Balance as of December 31, 2017	$ 686,108
Effect of foreign currency translation	(1,374)
Balance as of September 30, 2018	702,585
The Future Customer
Goodwill [Line Items]
Goodwill resulting from business combinations	7,597
DMS Disaster Consultants
Goodwill [Line Items]
Goodwill resulting from business combinations	$ 10,254

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 20
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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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No definition available.

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