Goodwill and Intangible Assets - Schedule of Goodwill by Reportable Segment (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($)
Goodwill [Line Items]
Goodwill at December 31, 2016	$ 1,555,850
Foreign exchange translation adjustment	603
Goodwill at March 31, 2017	1,556,453
Index [Member]
Goodwill [Line Items]
Goodwill at December 31, 2016	1,202,448
Foreign exchange translation adjustment	373
Goodwill at March 31, 2017	1,202,821
Analytics [Member]
Goodwill [Line Items]
Goodwill at December 31, 2016	302,611
Goodwill at March 31, 2017	302,611
All Other [Member]
Goodwill [Line Items]
Goodwill at December 31, 2016	50,791
Foreign exchange translation adjustment	230
Goodwill at March 31, 2017	$ 51,021

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant