Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
		Feb. 07, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassifications out of AOCI [Line Items]
Other Income (Expense)- Net	[1]	$ (86.0)	$ (122.7)	$ 8.1	$ (32.7)	$ 12.3
Tax benefit (expense)	[1]	27.5	27.5	23.1	101.8	60.1
Total after tax	[1]	(74.8)	(173.8)	(60.5)	(99.9)	(270.1)
Reclassification out of Accumulated Other Comprehensive Income
Reclassifications out of AOCI [Line Items]
Total before tax		3.8	0.0	0.0	(0.1)	0.0
Tax benefit (expense)		(1.0)	0.0	0.0	0.0	0.0
Total after tax		2.8	0.0	0.0	(0.1)	0.0
Net income (loss) attributable to Dun & Bradstreet Holdings, Inc. (Successor) / The Dun & Bradstreet Corporation (Predecessor)		2.8	0.0	0.0	(0.1)	0.0
Amortization of prior service costs | Reclassification out of Accumulated Other Comprehensive Income
Reclassifications out of AOCI [Line Items]
Other Income (Expense)- Net		(0.1)	0.0	0.0	(0.1)	0.0
Amortization of actuarial gain/loss | Reclassification out of Accumulated Other Comprehensive Income
Reclassifications out of AOCI [Line Items]
Other Income (Expense)- Net		$ 3.9	$ 0.0	$ 0.0	$ 0.0	$ 0.0

[1] See Note 1 "Basis of Presentation" for further discussion.