Annual report pursuant to Section 13 and 15(d)

QUARTERLY FINANCIAL DATA (UNAUDITED) (Additional Information) (Details)

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QUARTERLY FINANCIAL DATA (UNAUDITED) (Additional Information) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Quarterly Financial Data [Line Items]      
Tax Cuts and Jobs Act of 2017, income tax benefit $ 48.3    
Veda      
Quarterly Financial Data [Line Items]      
Acquisition related amounts     $ 40.2
Acquisition related amounts, net of tax     28.2
Cybersecurity Incident, Investigation, Remediation, Legal, And Other Professional Services      
Quarterly Financial Data [Line Items]      
Loss contingency, loss in period, net   $ 114.0  
Loss contingency, loss in period   113.3  
Selling, general and administrative expenses | Cybersecurity Incident, Investigation, Remediation, Legal, And Other Professional Services      
Quarterly Financial Data [Line Items]      
Loss contingency, loss in period, net   99.8  
Loss contingency, loss in period   99.1  
Cost of services | Cybersecurity Incident, Investigation, Remediation, Legal, And Other Professional Services      
Quarterly Financial Data [Line Items]      
Loss contingency, loss in period   $ 14.2  
Operating Income | Veda      
Quarterly Financial Data [Line Items]      
Acquisition related amounts     30.1
Other Income | Veda      
Quarterly Financial Data [Line Items]      
Acquisition related amounts     9.2
Interest Expense | Veda      
Quarterly Financial Data [Line Items]      
Acquisition related amounts     $ 0.7