Segment Information - Summary (Details) - USD ($) $ in Millions	3 Months Ended						6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020		Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 504.5	$ 479.9	$ 444.4	$ 418.7	$ 395.7	[1]	$ 814.4	$ 1,258.8	$ 1,738.7
Adjusted EBITDA	185.6				135.1
Depreciation and amortization	(149.7)				(134.4)	[1]
Interest expense - net	(48.8)				(82.7)
Dividends allocated to preferred stockholders	0.0				(32.0)	[1]
Benefit (provision) for income taxes	9.8	1.4	9.1	27.7	74.2	[1]	101.9	111.0	112.4
Other income (expense) - net	6.8				89.3	[1]
Equity in net income of affiliates	0.6				0.7	[1]
Net income (loss) attributable to non-controlling interest	(1.7)				(0.4)	[1]
Other incremental or reduced expenses and revenue from the application of purchase accounting and acquisitions	0.7				4.9
Equity-based compensation	(7.9)				(3.8)
Restructuring charges	(5.8)				(4.8)	[2]
Merger and acquisition-related operating costs	(3.1)				(2.5)
Transition costs	(0.6)				(1.6)
Legal reserve associated with significant legal and regulatory matters	(9.9)				0.0
Asset impairment	(1.0)				(0.1)
Net income (loss) attributable to Dun & Bradstreet Holdings, Inc.	(25.0)	$ 1.8	$ (16.3)	$ (208.0)	41.9	[1]	$ (166.1)	$ (182.4)	$ (180.6)
Capital expenditures	1.2				1.4	[2]
Additions to computer software and other intangibles	42.4				18.4
Operating Segments
Segment Reporting Information [Line Items]
Depreciation and amortization	(15.4)				(5.8)
Capital expenditures	1.2				1.3
Additions to computer software and other intangibles	42.2				18.0
Corporate and other
Segment Reporting Information [Line Items]
Revenue	(4.8)				(17.4)
Adjusted EBITDA	(16.9)				(33.4)
Depreciation and amortization	(134.3)				(128.6)
Capital expenditures	0.0				0.1
Additions to computer software and other intangibles	0.2				0.4
North America | Operating Segments
Segment Reporting Information [Line Items]
Revenue	339.4				341.5
Adjusted EBITDA	151.0				144.5
Depreciation and amortization	(12.6)				(4.7)
Capital expenditures	0.6				0.6
Additions to computer software and other intangibles	34.9				16.9
International | Operating Segments
Segment Reporting Information [Line Items]
Revenue	169.9				71.6
Adjusted EBITDA	51.5				24.0
Depreciation and amortization	(2.8)				(1.1)
Capital expenditures	0.6				0.7
Additions to computer software and other intangibles	$ 7.3				$ 1.1

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

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