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Goodwill and Other Intangible Assets, Net - Summary of Changes in Carrying Amount of Goodwill by Reportable Segment (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Goodwill [Line Items]
Beginning balance	$ 945,582
Acquisitions	38,439	$ 91,300
Measurement period adjustments	(2,432)
Cumulative translation adjustment	(1,962)
Ending balance	979,627	945,582
Financial Services [Member]
Goodwill [Line Items]
Beginning balance	468,050
Measurement period adjustments	12
Cumulative translation adjustment	(1,962)
Ending balance	466,100	468,050
Real Estate Services [Member]
Goodwill [Line Items]
Beginning balance	477,532
Acquisitions	38,439
Measurement period adjustments	(2,444)
Ending balance	$ 513,527	$ 477,532

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- Definition

Goodwill purchase accounting adjustments including prior period adjustments.

+ References

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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://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.

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-Publisher FASB
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-SubTopic 20
-Section 50
-Paragraph 1
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- Definition

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.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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