Take-Private Transaction - Purchase Price Allocation (Details) - USD ($) $ in Millions	6 Months Ended	11 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2019	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Feb. 08, 2019	Dec. 31, 2018
Preliminary Purchase Price Allocation:
Goodwill	$ 2,848.0	$ 2,840.1	$ 2,840.1	$ 2,850.8	$ 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				117.7
Accounts receivable		266.1	266.1				267.8
Other		46.4	46.4				46.8
Total current assets		430.2	430.2				432.3
Goodwill		2,787.6	2,787.6				2,797.6
Property, plant & equipment		30.3	30.3				30.3
Right of use asset		111.3	111.3				103.9
Other		34.3	34.3				34.4
Total assets acquired		9,386.3	9,386.3				9,333.3
Accounts payable		74.2	74.2				74.2
Deferred revenue		397.8	397.8				398.4
Accrued liabilities		237.8	237.8				240.1
Short-term pension and other accrued benefits		106.0	106.0				106.0
Other current liabilities		45.8	45.8				41.1
Total current liabilities		861.6	861.6				859.8
Long-term pension and postretirement obligations		221.0	221.0				213.6
Deferred tax liability		1,380.6	1,380.6				1,388.3
Long-term debt		625.1	625.1				625.1
Other liabilities		169.0	169.0				161.0
Total liabilities assumed		3,257.3	3,257.3				3,247.8
Non-controlling interest		60.3	60.3				16.8
Less: debt repayment		637.5	637.5				637.5
Amounts paid to equity holders		5,431.2	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	1,275.8				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	2,388.5				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	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				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	$ 1,722.0				$ 1,769.0
Measurement Period Adjustments
Intangible assets		$ (47.0)