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Acquired Intangible Assets Fair Value and Weighted-Average Useful Life (Detail)

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Acquired Intangible Assets Fair Value and Weighted-Average Useful Life (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Identifiable intangible assets (1) $ 524.7 [1] $ 52.2 [1]
Weighted-average useful life 14 years 8 months 12 days 6 years 10 months 24 days
Customer relationships
    
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Identifiable intangible assets (1) 4.5 29.9
Weighted-average useful life 8 years 8 months 12 days 8 years 9 months 18 days
Acquired software and technology
    
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Identifiable intangible assets (1) 0.7 13.4
Weighted-average useful life 5 years 8 months 12 days 4 years 2 months 12 days
Purchased data files
    
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Identifiable intangible assets (1) 508.8 3.2
Weighted-average useful life 15 years 5 years 2 months 12 days
Non-compete agreements
    
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Identifiable intangible assets (1) 10.3 2.3
Weighted-average useful life 4 years 10 months 24 days 3 years 8 months 12 days
Trade names and other intangible assets
    
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Identifiable intangible assets (1) $ 0.4 $ 3.4
Weighted-average useful life 5 years 5 years 6 months
[1] Identifiable intangible assets are further disaggregated in the following table.