Goodwill and Intangible Assets - Acquired Intangible Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	$ 875.5	$ 875.5
Accumulated Impairment Charges	(1.5)	(1.5)
Accumulated Amortization	(363.2)	(308.0)
Foreign Currency Translation	1.4	(1.4)
Intangible assets, net	512.2	564.6
Completed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	446.4	446.4
Accumulated Impairment Charges	(0.1)	(0.1)
Accumulated Amortization	(209.8)	(178.3)
Foreign Currency Translation	(0.1)	(0.2)
Intangible assets, net	236.4	267.8
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	308.2	308.2
Accumulated Impairment Charges	(1.4)	(1.4)
Accumulated Amortization	(104.8)	(84.2)
Foreign Currency Translation	1.7	(1.4)
Intangible assets, net	203.7	221.2
Patents, Trademarks, Trade Names and Other [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross	120.9	120.9
Accumulated Amortization	(48.6)	(45.5)
Foreign Currency Translation	(0.2)	0.2
Intangible assets, net	$ 72.1	$ 75.6