Investments in Unconsolidated Affiliates - Summarized Financial Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Current assets	$ 345.0		$ 345.0			$ 352.1
Total assets	5,928.5		5,928.5			6,350.9
Current liabilities, including short-term debt	284.4		284.4			264.8
Total liabilities	3,381.0		3,381.0			3,071.7
Total shareholders' equity	2,500.1	$ 2,664.2	2,500.1	$ 2,664.2	$ 2,451.0	2,090.4	$ 2,614.7	$ 2,627.7
Total liabilities, redeemable noncontrolling interests and shareholders' equity	5,928.5		5,928.5			6,350.9
Revenues	394.5	361.3	781.7	711.0
Loss before provision for income taxes and equity in net income of affiliates	52.0	47.7	109.9	92.0
Net loss	40.3	32.2	402.4	77.7
Net loss attributable to DNB	40.3	39.7	404.9	93.8
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Current assets	748.1		748.1			718.0
Non-current assets	8,948.5		8,948.5			9,279.2
Total assets	9,696.6		9,696.6			9,997.2
Current liabilities, including short-term debt	948.0		948.0			1,004.9
Non-current liabilities	5,102.9		5,102.9			5,247.0
Total liabilities	6,050.9		6,050.9			6,251.9
Total shareholders' equity	3,645.7		3,645.7			3,745.3
Total liabilities, redeemable noncontrolling interests and shareholders' equity	9,696.6		9,696.6			$ 9,997.2
Revenues	537.3	520.9	1,073.3	1,025.4
Loss before provision for income taxes and equity in net income of affiliates	(0.7)	(8.5)	(40.5)	(42.2)
Net loss		(50.8)	(29.8)	(74.1)
Net loss attributable to DNB	$ (1.8)	$ (51.7)	$ (33.1)	$ (76.7)