Goodwill And Intangible Assets (Summary Of Intangible Assets) (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 31.1
Finite-Lived Intangible Assets, Amortization Expense, Year Two	40.8
Finite-Lived Intangible Assets, Amortization Expense, Year Three	34.5
Gross Asset	823.6	$ 823.6
Accumulated Amortization	352.6	341.8
Net	471.0	481.8
Finite-Lived Intangible Assets, Net	471.0	481.8	$ 276.8
Finite-Lived Intangible Assets, Amortization Expense, Year Four	34.3
Finite-Lived Intangible Assets, Amortization Expense, Year Five	260.5
Intellectual Property Rights
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	130.7	130.7
Accumulated Amortization	55.9	55.6
Net	74.8	75.1
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	546.7	546.8
Accumulated Amortization	218.2	210.7
Net	328.5	336.1
Drawings
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	11.1	11.1
Accumulated Amortization	10.5	10.5
Net	0.6	0.6
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Asset	135.1	135.0
Accumulated Amortization	68.0	65.0
Net	$ 67.1	$ 70.0