Take-Private Transaction - Purchase Price Allocation (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	11 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Dec. 31, 2019	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Feb. 08, 2019	Dec. 31, 2018
Preliminary Purchase Price Allocation:
Goodwill	$ 2,850.8	$ 2,853.9	$ 2,840.1	$ 2,848.0	$ 2,967.4	$ 2,792.6	$ 2,797.6	$ 773.5	$ 0.0
Take Private Acquisition, Dun & Bradstreet
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)		16 years 6 months
Preliminary Purchase Price Allocation:
Cash			117.7					117.7
Accounts receivable			266.1					267.8
Other			46.4					46.8
Total current assets			430.2					432.3
Goodwill			2,787.6					2,797.6
Property, plant & equipment			30.3					30.3
Right of use asset			111.3					103.9
Other			34.3					34.4
Total assets acquired			9,386.3					9,333.3
Accounts payable			74.2					74.2
Deferred revenue			397.8					398.4
Accrued liabilities			237.8					240.1
Short-term pension and other accrued benefits			106.0					106.0
Other current liabilities			45.8					41.1
Total current liabilities			861.6					859.8
Long-term pension and postretirement obligations			221.0					213.6
Deferred tax liability			1,380.6					1,388.3
Long-term debt			625.1					625.1
Other liabilities			169.0					161.0
Total liabilities assumed			3,257.3					3,247.8
Non-controlling interest			60.3					16.8
Less: debt repayment			637.5					637.5
Amounts paid to equity holders			5,431.2					5,431.2
Measurement Period Adjustments
Accounts receivable			(1.7)
Other			(0.4)
Total current assets			(2.1)
Goodwill	$ (10.0)		(10.0)
Right of use asset			7.4
Other			(0.1)
Total assets acquired			53.0
Deferred revenue			(0.6)
Accrued liabilities			(2.3)
Other current liabilities			4.7
Total current liabilities			1.8
Long-term pension and postretirement obligations			7.4
Deferred tax liability			(7.7)
Other liabilities			8.0
Total liabilities assumed			9.5
Non-controlling interest			43.5
Take Private Acquisition, Dun & Bradstreet | Trademark
Preliminary Purchase Price Allocation:
Intangible assets			1,275.8					1,200.8
Measurement Period Adjustments
Intangible assets			75.0
Take Private Acquisition, Dun & Bradstreet | Customer relationships
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)		16 years 10 months 24 days
Preliminary Purchase Price Allocation:
Intangible assets			2,388.5					2,589.0
Measurement Period Adjustments
Intangible assets			(200.5)
Take Private Acquisition, Dun & Bradstreet | Partnership agreements
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)		14 years 3 months 18 days
Preliminary Purchase Price Allocation:
Intangible assets			230.3					0.0
Measurement Period Adjustments
Intangible assets			230.3
Take Private Acquisition, Dun & Bradstreet | Computer software
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)		7 years 9 months 18 days
Preliminary Purchase Price Allocation:
Intangible assets			376.0					376.0
Take Private Acquisition, Dun & Bradstreet | Database
Business Acquisition [Line Items]
Weighted Average Amortization Period (years)		17 years
Preliminary Purchase Price Allocation:
Intangible assets			1,722.0					$ 1,769.0
Measurement Period Adjustments
Intangible assets			$ (47.0)