Goodwill and Other Intangible Assets, net - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule of Other Intangible Assets by Major Class [Line Items]
Gain (loss) on disposition of business		$ (0.1)	$ 0.0	$ (6.9)	$ 0.0
Amortization expense		18.7	$ 18.5	59.4	$ 56.2
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2021		20.1		20.1
2022		72.9		72.9
2023		68.2		68.2
2024		63.3		63.3
2025		58.8		58.8
2026		$ 55.1		$ 55.1
Percentage of definite-lived intangible assets under accelerated amortization method (approximate)		76.00%		76.00%
Consumer Analytics Solutions Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Schedule of Other Intangible Assets by Major Class [Line Items]
Discontinued operation consideration	$ 9.8
Dispositions, assets	15.9
Dispositions, definite-lived intangibles	8.7
Dispositions, goodwill	1.9
Dispositions, liabilities	1.5
Gain (loss) on disposition of business	$ (6.9)