Acquisitions - Pro Forma Information (Details) - USD ($) $ in Millions	3 Months Ended					6 Months Ended			9 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020		Jun. 30, 2021	Jun. 30, 2020		Sep. 30, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
Revenue	$ 520.9	$ 479.9	$ 444.4	$ 418.7	[1]	$ 1,025.4	$ 814.4	[1]	$ 1,258.8	$ 1,738.7
Total pro forma revenue	520.9			499.4		1,030.0	979.5
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	(51.7)			(208.0)		(76.7)	(166.1)
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	(51.7)	$ 1.8	$ (16.3)	(208.0)	[1]	(76.7)	(166.1)	[1]	$ (182.4)	$ (180.6)
Pro forma net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	(52.5)			(205.8)		(74.2)	(174.4)
Adjustments to Bisnode pre-acquisition revenue related to revenue received from Dun & Bradstreet Holdings, Inc.
Business Acquisition [Line Items]
Revenue	0.0			(4.2)		0.0	(8.3)
Adjustments to Dun & Bradstreet revenue related to revenue received from Bisnode
Business Acquisition [Line Items]
Revenue	0.0			(8.6)		0.0	(17.0)
Pre-acquisition net income - Bisnode
Business Acquisition [Line Items]
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	0.0			15.0		0.8	16.1
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	0.0			15.0		0.8	16.1
Intangible amortization - net of tax benefits
Business Acquisition [Line Items]
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	(0.8)			(12.8)		(0.9)	(25.6)
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	(0.8)			(12.8)		(0.9)	(25.6)
Write off related to pre-existing relationship - net of tax benefits
Business Acquisition [Line Items]
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	0.0			0.0		2.3	(2.3)
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	0.0			0.0		2.3	(2.3)
Transaction costs - net of tax benefits
Business Acquisition [Line Items]
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	0.0			0.0		0.3	3.5
Reported net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	0.0			0.0		0.3	3.5
Bisnode
Business Acquisition [Line Items]
Revenue	$ 0.0			$ 93.5		$ 4.6	$ 190.4

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