Segment Information - Schedule of Revenue and Operating Income (Loss) by Segment (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended					6 Months Ended			9 Months Ended	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020		Jun. 30, 2021	Jun. 30, 2020		Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenue		$ 520.9	$ 479.9	$ 444.4	$ 418.7	[1]	$ 1,025.4	$ 814.4	[1]	$ 1,258.8	$ 1,738.7
Adjusted EBITDA		198.3			176.1		384.0	311.2
Depreciation and amortization		(152.3)			(132.7)	[1]	(302.0)	(267.1)	[1]
Interest expense - net		(47.8)			(77.8)		(96.6)	(160.5)
Dividends allocated to preferred stockholders		0.0			(32.1)	[1]	0.0	(64.1)	[1]
Benefit (provision) for income taxes		(43.0)	1.4	9.1	27.7	[1]	(33.2)	101.9	[1]	111.0	112.4
Other income (expense) - net		12.4			(122.9)	[1]	19.2	(33.6)	[1]
Equity in net income of affiliates		0.7			0.6	[1]	1.3	1.3	[1]
Net income (loss) attributable to non-controlling interest		(0.9)			(1.2)	[1]	(2.6)	(1.6)	[1]
Other incremental or reduced expenses and revenue from the application of purchase accounting and acquisitions		4.2			4.9		4.9	9.8
Equity-based compensation		(7.1)			(25.1)		(14.7)	(28.9)
Restructuring charges		(10.1)			(7.1)	[1]	(15.9)	(11.9)	[2]
Merger and acquisition-related operating costs		(2.0)			(1.9)		(5.1)	(4.4)
Transition costs		(2.9)			(16.3)		(3.9)	(17.9)
Legal reserve associated with significant legal and regulatory matters		(0.7)			0.0		(10.6)	0.0
Asset impairment		(0.5)			(0.2)		(1.5)	(0.3)
Net income (loss) attributable to Dun & Bradstreet Holdings, Inc., Basic		(51.7)	$ 1.8	$ (16.3)	(208.0)	[1]	(76.7)	(166.1)	[1]	$ (182.4)	$ (180.6)
Capital expenditures		79.4			2.5		80.7	4.0
Additions to computer software and other intangibles		34.1			29.7		76.5	48.1
In-place lease intangibles	$ 7.1	7.1					7.1
Office Building In Jacksonville, FL
Segment Reporting Information [Line Items]
Asset acquisition, purchase price	76.6
In-place lease intangibles	$ 7.1	7.1					7.1
Operating Segments
Segment Reporting Information [Line Items]
Depreciation and amortization		(17.4)			(13.3)		(32.8)	(25.7)
Capital expenditures		79.3			2.5		80.6	3.9
Additions to computer software and other intangibles		33.8			29.1		76.1	47.1
Corporate and other
Segment Reporting Information [Line Items]
Revenue		0.0			(2.1)		(4.8)	(19.5)
Adjusted EBITDA		(11.7)			(14.3)		(28.6)	(47.7)
Depreciation and amortization		(134.9)			(119.4)		(269.2)	(241.4)
Capital expenditures		0.1			0.0		0.1	0.1
Additions to computer software and other intangibles		0.3			0.6		0.4	1.0
North America | Operating Segments
Segment Reporting Information [Line Items]
Revenue		357.2			354.4		696.6	695.9
Adjusted EBITDA		167.4			170.4		318.5	314.9
Depreciation and amortization		(14.6)			(11.3)		(27.2)	(22.0)
Capital expenditures		77.7			0.9		78.3	1.5
Additions to computer software and other intangibles		27.5			27.4		62.4	44.3
International | Operating Segments
Segment Reporting Information [Line Items]
Revenue		163.7			66.4		333.6	138.0
Adjusted EBITDA		42.6			20.0		94.1	44.0
Depreciation and amortization		(2.8)			(2.0)		(5.6)	(3.7)
Capital expenditures		1.6			1.6		2.3	2.4
Additions to computer software and other intangibles		$ 6.3			$ 1.7		$ 13.7	$ 2.8

[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.