Quarterly report pursuant to Section 13 or 15(d)

GOODWILL AND INTANGIBLE ASSETS - Purchased Intangible Assets (Details)

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GOODWILL AND INTANGIBLE ASSETS - Purchased Intangible Assets (Details) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross $ 1,871.5 $ 2,000.1
Accumulated Amortization (716.6) (753.1)
Net 1,154.9 1,247.0
Purchased data files    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 925.9 955.7
Accumulated Amortization (277.4) (262.2)
Net 648.5 693.5
Acquired software and technology    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 122.7 142.3
Accumulated Amortization (62.7) (66.6)
Net 60.0 75.7
Customer relationships    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 701.0 772.4
Accumulated Amortization (279.4) (326.7)
Net 421.6 445.7
Reacquired rights    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 73.3 73.3
Accumulated Amortization (72.2) (65.6)
Net 1.1 7.7
Proprietary database    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 24.0 22.1
Accumulated Amortization (9.9) (8.7)
Net 14.1 13.4
Non-compete agreements    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 4.4 14.1
Accumulated Amortization (3.1) (12.7)
Net 1.3 1.4
Trade names and other intangible assets    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 20.2 20.2
Accumulated Amortization (11.9) (10.6)
Net $ 8.3 $ 9.6