Annual report pursuant to Section 13 and 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.20.4
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
shares in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
segment
shares
Dec. 31, 2019
USD ($)
shares
Dec. 31, 2018
USD ($)
shares
Jan. 01, 2018
USD ($)
Dec. 31, 2017
USD ($)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Number of reportable segments | segment 4        
Number of operating segments | segment 4        
Contract assets $ 11,000,000.0        
Advertising costs from continuing operations 59,000,000.0 $ 51,900,000 $ 43,100,000    
Depreciation and amortization 399,300,000 337,300,000 315,900,000    
Fixed assets, pledged as collateral 156,400,000 156,400,000      
Goodwill and intangible asset impairment 0 0 0    
Carrying value of investment 127,700,000        
Unrealized gain on investment 116,600,000        
Foreign currency transaction loss 7,500,000 3,000,000.0 1,600,000    
Fair value of debt 4,800,000,000 3,600,000,000      
Long term debt carrying amount 4,400,000,000 3,400,000,000      
Variable interest entity, maximum exposure to loss $ 26,800,000        
Variable interest entity, ownership percentage 75.00%        
Redemption premium $ 0        
Cumulative effect of change in accounting principle 3,210,300,000 2,622,900,000 3,155,600,000   $ 3,239,000,000.0
Cumulative adjustment from change in accounting principle          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Cumulative effect of change in accounting principle   (400,000)     4,200,000
Property and Equipment          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Depreciation and amortization $ 249,300,000 191,000,000.0 $ 157,600,000    
Minimum | Computer Software Intangible Asset          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 3 years        
Maximum | Computer Software Intangible Asset          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 10 years        
Data Processing Equipment Capitalized Internal Use Software and Systems Costs | Minimum          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 3 years        
Data Processing Equipment Capitalized Internal Use Software and Systems Costs | Maximum          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 10 years        
Building          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 40 years        
Other Capitalized Property Plant and Equipment | Minimum          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 3 years        
Other Capitalized Property Plant and Equipment | Maximum          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Property, plant and equipment useful life 7 years        
Other Current Assets          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Insurance settlements receivable $ 112,400,000        
Income taxes receivable, current 21,300,000 35,600,000      
Restricted cash 25,100,000 29,300,000      
Other Current Liabilities          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Restricted cash 25,100,000 29,300,000      
Legal fees $ 379,700,000 $ 589,000,000.0      
Stock Options          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Antidilutive stock options excluded from computation of earnings per share (in shares) | shares 0.4 1.1 0.7    
U.S. Information Solutions | Revenue Benchmark          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Largest segment's percent of total operating revenue (as a percent) 36.00%        
Retained Earnings          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Cumulative effect of change in accounting principle $ 4,185,400,000 $ 3,854,600,000 $ 4,425,900,000   4,600,600,000
Retained Earnings | Cumulative adjustment from change in accounting principle          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Cumulative effect of change in accounting principle (284,100,000) (400,000) (291,900,000) $ (302,600,000) (298,400,000)
Accumulated Other Comprehensive Loss          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Cumulative effect of change in accounting principle (171,400,000) (354,400,000) (334,500,000)   (412,000,000.0)
Accumulated Other Comprehensive Loss | Cumulative adjustment from change in accounting principle          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Cumulative effect of change in accounting principle 284,100,000 277,200,000 291,900,000   $ 302,600,000
Cybersecurity Incident | Other Current Liabilities          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Legal fees 355,200,000 563,900,000      
Other Income          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Foreign currency transaction loss $ 500,000 $ 1,000,000.0 $ 1,800,000