Investments in Unconsolidated Affiliates - Summarized Financial Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Current assets	$ 299.1		$ 299.1			$ 352.1
Total assets	5,838.0		5,838.0			6,350.9
Current liabilities, including short-term debt	260.8		260.8			264.8
Total liabilities	3,246.1		3,246.1			3,071.7
Total shareholders' equity	2,549.1	$ 2,253.0	2,549.1	$ 2,253.0	$ 2,500.1	2,090.4	$ 2,664.2	$ 2,627.7
Total liabilities, redeemable noncontrolling interests and shareholders' equity	5,838.0		5,838.0			6,350.9
Revenues	386.7	378.0	1,168.4	1,089.0
Income (loss) before provision for income taxes and equity in net income of affiliates	36.2	60.0	146.1	152.0
Net income (loss)	30.0	46.3	432.4	124.0
Net income (loss) attributable to DNB	30.0	53.4	434.9	147.2
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Current assets	666.6		666.6			718.0
Non-current assets	8,763.1		8,763.1			9,279.2
Total assets	9,429.7		9,429.7			9,997.2
Current liabilities, including short-term debt	936.4		936.4			1,004.9
Non-current liabilities	4,905.7		4,905.7			5,247.0
Total liabilities	5,842.1		5,842.1			6,251.9
Total shareholders' equity	3,587.6		3,587.6			3,745.3
Total liabilities, redeemable noncontrolling interests and shareholders' equity	9,429.7		9,429.7			$ 9,997.2
Revenues	556.3	541.9	1,629.6	1,567.3
Income (loss) before provision for income taxes and equity in net income of affiliates	5.7	14.7	(34.8)	(27.5)
Net income (loss)	10.4	18.2	(19.4)	(55.9)
Net income (loss) attributable to DNB	$ 8.0	$ 16.6	$ (25.1)	$ (60.1)