Introduction and Basis of Presentation - Additional Information (Detail) - Operating Revenues [Member] - Customer Concentration Risk [Member]	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer	10.00%
Blackrock Inc [Member] \| Maximum [Member]
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer		10.40%
Index [Member] \| Blackrock Inc [Member]
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer	17.10%	19.50%
Analytics [Member]
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer	10.00%	10.00%
All Other [Member]
Introduction And Basis Of Presentation [Line Items]
Percentage of operating revenues accounted for by major customer	10.00%	10.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611

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