Business Combinations, Goodwill and Intangible Assets - Summary of Company's Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning Balance	$ 186,770	$ 171,535
Acquisitions	15,957	16,108
Currency translation adjustments	1,754	(873)
Ending Balance	204,481	186,770
Insurance
Goodwill [Roll Forward]
Beginning Balance	38,110	35,824
Acquisitions	0	2,510
Currency translation adjustments	223	(224)
Ending Balance	38,333	38,110
Healthcare
Goodwill [Roll Forward]
Beginning Balance	19,276	19,276
Acquisitions	15,957	0
Currency translation adjustments	0	0
Ending Balance	35,233	19,276
TT&L
Goodwill [Roll Forward]
Beginning Balance	12,983	13,278
Acquisitions	0	0
Currency translation adjustments	696	(295)
Ending Balance	13,679	12,983
F&A
Goodwill [Roll Forward]
Beginning Balance	47,537	47,891
Acquisitions	0	0
Currency translation adjustments	835	(354)
Ending Balance	48,372	47,537
All Other
Goodwill [Roll Forward]
Beginning Balance	5,326	5,326
Acquisitions	0	0
Currency translation adjustments	0	0
Ending Balance	5,326	5,326
Analytics
Goodwill [Roll Forward]
Beginning Balance	63,538	49,940
Acquisitions	0	13,598
Currency translation adjustments	0	0
Ending Balance	$ 63,538	$ 63,538

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://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=64834752&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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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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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