Annual report pursuant to Section 13 and 15(d)

ACQUISITIONS AND INVESTMENTS (Acquired Intangible Assets Fair Value and Weighted-Average Useful Life) (Details)

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ACQUISITIONS AND INVESTMENTS (Acquired Intangible Assets Fair Value and Weighted-Average Useful Life) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Business Acquisition [Line Items]    
Fair value $ 51.0 $ 681.0
Weighted-average useful life 9 years 6 months 12 years 10 months 24 days
Customer relationships    
Business Acquisition [Line Items]    
Fair value $ 42.7 $ 171.3
Weighted-average useful life 10 years 2 months 14 years 10 months 24 days
Acquired software and technology    
Business Acquisition [Line Items]    
Fair value $ 6.5 $ 106.3
Weighted-average useful life 6 years 6 months 4 years 2 months 12 days
Purchased data files    
Business Acquisition [Line Items]    
Fair value $ 0.0 $ 387.5
Weighted-average useful life   14 years 9 months 18 days
Non-compete agreements    
Business Acquisition [Line Items]    
Fair value 0.0 $ 5.4
Weighted-average useful life   2 years 1 month 6 days
Trade names and other intangible assets    
Business Acquisition [Line Items]    
Fair value $ 1.8 $ 10.5
Weighted-average useful life 2 years 11 months 1 year