Annual report pursuant to Section 13 and 15(d)

BENEFIT PLANS (Additional Information) (Details)

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BENEFIT PLANS (Additional Information) (Details)
 12 Months Ended
Dec. 31, 2017
USD ($)
plan
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2015
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Number of executive defined benefit pension plans | plan 2    
Number of executive retirement programs | plan 2    
Accumulated benefit obligation $ 722,300,000 $ 685,300,000  
Difference between actual returns and expected returns rate over five years period 20.00%    
Hedge funds, minimum number of days notice prior to redemption 30 days    
Hedge funds, maximum number of days notice prior to redemption 90 days    
Cost recognized $ 29,700,000 27,100,000 $ 23,200,000
Accrued incentive compensations $ 44,900,000 $ 90,000,000  
Stock held by employee benefits trusts, shares (in shares) | shares 600,000 600,000.0  
Equifax stock included in Employee Benefit Trusts at cost $ 5,900,000 $ 5,900,000  
Minimum      
Defined Benefit Plan Disclosure [Line Items]      
Discretionary match of participants' contributions, dependent on certain eligibility rules 400.00%    
Maximum      
Defined Benefit Plan Disclosure [Line Items]      
Discretionary match of participants' contributions, dependent on certain eligibility rules 600.00%    
Private Equity      
Defined Benefit Plan Disclosure [Line Items]      
Commitments related to investments $ 10,700,000 12,300,000  
Real Assets      
Defined Benefit Plan Disclosure [Line Items]      
Commitments related to investments 500,000 500,000  
Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions $ 5,900,000 5,200,000  
Pension Benefits | U.S.      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan percentage of employees covered 15.00%    
Employer contributions $ 0 0  
Pension plans investment return 17.90%    
Defined benefit plan expected return 7.25%    
Expected return on plan assets for 2018 7.25%    
Pension Benefits | Canada      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions $ 1,500,000 800,000  
Pension plans investment return 7.80%    
Defined benefit plan expected return 6.00%    
Expected return on plan assets for 2018 6.00%    
Other Postretirement Benefit Plans      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions $ 2,200,000 2,600,000  
Other Postretirement Benefit Plans | U.S.      
Defined Benefit Plan Disclosure [Line Items]      
Plans with projected benefit obligations and accumulated benefits benefit obligations in excess of plan's respective assets, projected benefit obligation 675,200,000 643,400,000  
Plans with projected benefit obligations and accumulated benefits benefit obligations in excess of plan's respective assets, accumulated benefit obligation 673,100,000 641,600,000  
Plans with projected benefit obligations and accumulated benefits benefit obligations in excess of plan's respective assets, fair value of plan assets $ 510,900,000 $ 468,300,000  
Initial annual rate increase in the per capita cost of covered healthcare benefits 6.70% 7.00%  
Ultimate annual rate decrease in the per capita cost of of covered healthcare benefits 5.00%    
Other Postretirement Benefit Plans | Canada      
Defined Benefit Plan Disclosure [Line Items]      
Plans with projected benefit obligations and accumulated benefits benefit obligations in excess of plan's respective assets, projected benefit obligation $ 56,400,000 $ 50,200,000  
Plans with projected benefit obligations and accumulated benefits benefit obligations in excess of plan's respective assets, accumulated benefit obligation 49,200,000 43,700,000  
Plans with projected benefit obligations and accumulated benefits benefit obligations in excess of plan's respective assets, fair value of plan assets $ 50,200,000 47,000,000  
Initial annual rate increase in the per capita cost of covered healthcare benefits 5.50%    
Ultimate annual rate decrease in the per capita cost of of covered healthcare benefits 5.00%    
Other Postretirement Benefit Plans | Foreign Plan      
Defined Benefit Plan Disclosure [Line Items]      
Cost recognized $ 7,300,000 $ 5,900,000 $ 700,000