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
Mar. 31, 2018
Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross $ 1,995.6 $ 2,000.1
Accumulated Amortization (776.4) (753.1)
Net 1,219.2 1,247.0
Purchased data files    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 953.5 955.7
Accumulated Amortization (272.5) (262.2)
Net 681.0 693.5
Acquired software and technology    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 144.0 142.3
Accumulated Amortization (75.1) (66.6)
Net 68.9 75.7
Customer relationships    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 776.2 772.4
Accumulated Amortization (336.0) (326.7)
Net 440.2 445.7
Reacquired rights    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 73.3 73.3
Accumulated Amortization (68.9) (65.6)
Net 4.4 7.7
Proprietary database    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 23.2 22.1
Accumulated Amortization (9.2) (8.7)
Net 14.0 13.4
Non-compete agreements    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 4.4 14.1
Accumulated Amortization (3.0) (12.7)
Net 1.4 1.4
Trade names and other intangible assets    
Acquired Finite-Lived Intangible Assets [Line Items]    
Gross 21.0 20.2
Accumulated Amortization (11.7) (10.6)
Net $ 9.3 $ 9.6