Goodwill And Intangible Assets (Summary Of Intangible Assets) (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 10.9
Finite-Lived Intangible Assets, Amortization Expense, Year Two	41.2
Finite-Lived Intangible Assets, Amortization Expense, Year Three	37.1
Gross Asset	825.5	$ 579.3
Accumulated Amortization	333.4	302.5
Net	492.1	276.8
Finite-Lived Intangible Assets, Net	492.1	276.8	$ 282.2
Finite-Lived Intangible Assets, Amortization Expense, Year Four	34.7
Finite-Lived Intangible Assets, Amortization Expense, Year Five	298.0
Intellectual Property Rights
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	131.5	91.7
Accumulated Amortization	55.7	54.8
Net	75.8	36.9
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	547.7	414.7
Accumulated Amortization	204.8	183.4
Net	342.9	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	135.2	61.8
Accumulated Amortization	62.5	53.9
Net	$ 72.7	$ 7.9