Acquisitions - Purchase Price Allocation (Details) - USD ($) $ in Millions				6 Months Ended	9 Months Ended			12 Months Ended
	Nov. 15, 2021	Nov. 05, 2021	Jan. 08, 2021	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020		Dec. 31, 2021	Mar. 31, 2021	Mar. 31, 2020	Jul. 01, 2019
Initial purchase price allocation:
Goodwill				$ 2,841.7	$ 3,493.3	$ 2,857.9	[1]	$ 3,493.3
Eyeota
Initial purchase price allocation:
Cash		$ 7.1
Accounts receivable		9.3
Other		0.5
Total current assets		$ 16.9
Amortization life (years)		2 years
Goodwill		$ 138.3
Total assets acquired		190.2
Deferred tax liability		5.9
Other liabilities		12.0
Total liabilities assumed		17.9
Total purchase price		$ 172.3
Orb Intelligence & coAction.com
Initial purchase price allocation:
Cash						0.5				$ 0.5
Accounts receivable						0.3				0.3
Other						0.3				0.2
Total current assets						1.1				1.0
Goodwill						10.9				10.7
Deferred tax asset						0.4				0.4
Total assets acquired						21.6				21.3
Total liabilities assumed						0.4				0.2
Total purchase price						21.2				21.1
Measurement period adjustments
Cash					0.0
Accounts receivable					0.0
Other current assets						0.1
Total current assets						0.1
Goodwill						0.2
Deferred tax asset						0.0
Total assets acquired						0.3
Total liabilities assumed						0.2
Total purchase price						0.1
Bisnode
Initial purchase price allocation:
Cash					29.9			29.9	$ 29.9
Accounts receivable					61.0			61.0	61.0
Other					13.1			13.1	13.1
Total current assets					104.0			104.0	104.0
Property, plant & equipment					3.5			3.5	3.5
Goodwill					495.4			495.4	488.4
Right of use asset					27.4			27.4	26.7
Other					2.9			2.9	5.2
Total assets acquired					1,186.2			1,186.2	1,185.8
Accounts payable					17.5			17.5	17.5
Deferred revenue					80.6			80.6	80.6
Accrued payroll					20.7			20.7	20.7
Accrued income tax and other tax liabilities					17.1			17.1	17.1
Short-term lease liability					8.6			8.6	8.4
Other current liabilities					23.7			23.7	23.7
Total current liabilities					168.2			168.2	168.0
Long-term pension and postretirement obligations					65.4			65.4	65.4
Deferred tax liability					127.8			127.8	127.6
Long-term lease liability					18.2			18.2	18.2
Other liabilities					0.8			0.8	0.8
Total liabilities assumed					380.4			380.4	380.0
Total purchase price					805.8			805.8	805.8
Measurement period adjustments
Cash					0.0
Accounts receivable					0.0
Other current assets					0.0
Total current assets					0.0
Property, plant & equipment					0.0
Goodwill					7.0
Right of use asset					0.7
Other					(2.3)
Total assets acquired					0.4
Deferred tax liability					0.2
Long-term lease liability					0.0
Accounts payable					0.0
Deferred revenue					0.0
Accrued payroll					0.0
Accrued income tax and other tax liabilities					0.0
Short-term lease liability					0.2
Other current liabilities					0.0
Total current liabilities					0.2
Long-term pension and postretirement obligations					0.0
Other liabilities					0.0
Total liabilities assumed					0.4
Total consideration					0.0
Lattice
Initial purchase price allocation:
Cash						0.1					$ 0.1
Accounts receivable						1.9					1.9
Other						0.7					0.7
Total current assets						2.7					2.7
Goodwill						55.2					43.0
Deferred tax asset						17.5					18.4
Other						0.5					0.7
Total assets acquired						137.8					137.9
Deferred revenue						6.5					6.5
Other liabilities						4.3					4.4
Total liabilities assumed						10.8					10.9
Total purchase price						127.0					127.0
Measurement period adjustments
Cash				0.0
Accounts receivable				0.0
Other current assets				0.0
Total current assets				0.0
Goodwill				12.2
Other				(0.2)
Deferred tax asset				(0.9)
Total assets acquired				(0.1)
Deferred revenue				0.0
Other liabilities				(0.1)
Total liabilities assumed				(0.1)
Total purchase price				0.0
NetWise
Initial purchase price allocation:
Cash	$ 2.6
Accounts receivable	2.6
Other	0.4
Total current assets	5.6
Goodwill	41.9
Total assets acquired	71.0
Total liabilities assumed	1.2
Total purchase price	$ 69.8
Reacquired right | Bisnode
Business Acquisition [Line Items]
Amortization life (years)			15 years
Initial purchase price allocation:
Intangible assets:					270.0			270.0	271.0
Measurement period adjustments
Intangible assets:					(1.0)
Database | Bisnode
Business Acquisition [Line Items]
Amortization life (years)			12 years
Initial purchase price allocation:
Intangible assets:					111.0			$ 111.0	116.0
Measurement period adjustments
Intangible assets:					(5.0)
Database | NetWise
Initial purchase price allocation:
Amortization life (years)	3 years
Intangible assets:	$ 2.2
Customer relationships | Eyeota
Initial purchase price allocation:
Amortization life (years)		14 years
Intangible assets:		$ 20.0
Customer relationships | Orb Intelligence & coAction.com
Business Acquisition [Line Items]
Amortization life (years)								7 years
Initial purchase price allocation:
Intangible assets:						2.4				2.4
Measurement period adjustments
Intangible assets:						0.0
Customer relationships | Bisnode
Business Acquisition [Line Items]
Amortization life (years)			10 years
Initial purchase price allocation:
Intangible assets:					108.0			$ 108.0	106.0
Measurement period adjustments
Intangible assets:					2.0
Customer relationships | Lattice
Business Acquisition [Line Items]
Amortization life (years)								11 years
Initial purchase price allocation:
Intangible assets:						14.5					25.1
Measurement period adjustments
Intangible assets:				(10.6)
Customer relationships | NetWise
Initial purchase price allocation:
Amortization life (years)	15 years
Intangible assets:	$ 19.8
Technology | Eyeota
Initial purchase price allocation:
Amortization life (years)		5 years
Intangible assets:		$ 14.0
Technology | Orb Intelligence & coAction.com
Business Acquisition [Line Items]
Amortization life (years)								11 years
Initial purchase price allocation:
Intangible assets:						6.8				$ 6.8
Measurement period adjustments
Intangible assets:						0.0
Technology | Bisnode
Business Acquisition [Line Items]
Amortization life (years)			14 years
Initial purchase price allocation:
Intangible assets:					64.0			$ 64.0	$ 65.0
Measurement period adjustments
Intangible assets:					$ (1.0)
Technology | Lattice
Business Acquisition [Line Items]
Amortization life (years)								14 years
Initial purchase price allocation:
Intangible assets:						$ 47.4					$ 48.0
Measurement period adjustments
Intangible assets:				$ (0.6)
Technology | NetWise
Initial purchase price allocation:
Amortization life (years)	5 years
Intangible assets:	$ 1.3
Trademark | Eyeota
Initial purchase price allocation:
Intangible assets:		$ 1.0
Trademark | NetWise
Initial purchase price allocation:
Amortization life (years)	2 years
Intangible assets:	$ 0.2

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