Goodwill And Intangible Assets (Summary Of Intangible Assets) (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 33.8
Finite-Lived Intangible Assets, Amortization Expense, Year Two	41.9
Finite-Lived Intangible Assets, Amortization Expense, Year Three	37.7
Gross Asset	838.1	$ 579.3
Accumulated Amortization	317.1	302.5
Net	521.0	276.8
Finite-Lived Intangible Assets, Net	521.0	276.8	$ 282.2
Finite-Lived Intangible Assets, Amortization Expense, Year Four	34.9
Finite-Lived Intangible Assets, Amortization Expense, Year Five	301.7
Intellectual Property Rights
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	133.3	91.7
Accumulated Amortization	55.8	54.8
Net	77.5	36.9
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	557.5	414.7
Accumulated Amortization	193.4	183.4
Net	364.1	231.3
Drawings
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	11.1	11.1
Accumulated Amortization	10.4	10.4
Net	0.7	0.7
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	136.2	61.8
Accumulated Amortization	57.5	53.9
Net	$ 78.7	$ 7.9