Goodwill And Intangible Assets (Summary Of Intangible Assets) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	17 years 9 months 18 days
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 33.3
Finite-Lived Intangible Assets, Amortization Expense, Year Two	42.9
Finite-Lived Intangible Assets, Amortization Expense, Year Three	42.8
Intangible assets, net	503.0	$ 520.3	$ 505.1
Finite-Lived Intangible Assets, Accumulated Amortization	445.5	437.5
Finite-Lived Intangible Assets, Amortization Expense, Year Four	42.0
Intangible Assets, Gross (Excluding Goodwill)	948.5	957.8
Finite-Lived Intangible Assets, Amortization Expense, After Year Four	$ 271.0
Intellectual Property Rights
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years 2 months 12 days
Intangible assets, net	$ 79.1	79.8
Finite-Lived Intangible Assets, Accumulated Amortization	58.6	58.4
Intangible Assets, Gross (Excluding Goodwill)	$ 137.7	138.2
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	18 years 4 months 24 days
Intangible assets, net	$ 368.4	383.0
Finite-Lived Intangible Assets, Accumulated Amortization	287.8	280.6
Intangible Assets, Gross (Excluding Goodwill)	$ 656.2	663.6
Drawings
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	40 years
Intangible assets, net	$ 0.6	0.6
Finite-Lived Intangible Assets, Accumulated Amortization	10.5	10.5
Intangible Assets, Gross (Excluding Goodwill)	$ 11.1	11.1
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	11 years 8 months 12 days
Intangible assets, net	$ 54.9	56.9
Finite-Lived Intangible Assets, Accumulated Amortization	88.6	88.0
Intangible Assets, Gross (Excluding Goodwill)	$ 143.5	$ 144.9