Acquisitions - Purchase Price Allocation (Details) - USD ($) $ in Millions	Jan. 08, 2021	Mar. 31, 2021	Dec. 31, 2020	[1]	Mar. 31, 2020	Dec. 31, 2019
Purchase Price Allocation:
Goodwill		$ 3,318.2	$ 2,857.9		$ 2,848.7	$ 2,841.7
Bisnode
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)	13 years 7 months 6 days
Purchase Price Allocation:
Cash	$ 29.9
Accounts receivable	61.0
Other current assets	13.1
Total current assets	104.0
Property, plant, and equipment	3.5
Goodwill	488.4
Right of use asset	26.7
Other	5.2
Total assets acquired	1,185.8
Accounts payable	17.5
Deferred revenue	80.6
Accrued liabilities	20.7
Short-term pension and other accrued benefits	17.1
Short-term lease liability	8.4
Other current liabilities	23.7
Total current liabilities	168.0
Long-term pension and postretirement obligations	65.4
Deferred tax liability	127.6
Long-term debt	18.2
Other liabilities	0.8
Total liabilities assumed	380.0
Total purchase price	$ 805.8
Bisnode | Reacquired right
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)	15 years
Purchase Price Allocation:
Finite-lived intangible assets acquired	$ 271.0
Bisnode | Database
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)	12 years
Purchase Price Allocation:
Finite-lived intangible assets acquired	$ 116.0
Bisnode | Customer relationships
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)	10 years
Purchase Price Allocation:
Finite-lived intangible assets acquired	$ 106.0
Bisnode | Technology
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)	14 years
Purchase Price Allocation:
Finite-lived intangible assets acquired	$ 65.0

[1] See discussion in Note 1 - Basis of Presentation for further detail regarding the elimination of the International lag reporting.