Commitments and Contingencies (Schedule Of Activity Related To Asbestos Claim) (Detail)	3 Months Ended					12 Months Ended
	Mar. 31, 2019 USD ($) Claim	Mar. 31, 2018 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2017 USD ($)	Oct. 06, 2016 USD ($)	Apr. 22, 2016 USD ($)	Feb. 09, 2016 USD ($)	Jul. 02, 2015 USD ($)	Jun. 16, 2014 USD ($)	Sep. 17, 2013 USD ($)	Mar. 01, 2013 USD ($)	Feb. 25, 2013 USD ($)	Feb. 23, 2011 USD ($)	Mar. 23, 2010 USD ($)
Loss Contingencies [Line Items]
Document Period End Date	Mar. 31, 2019
Current asbestos liability	$ 66,000,000					$ 66,000,000
Payments for asbestos-related fees and costs, net of insurance recoveries	$ 9,700,000	$ 2,900,000
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Asbestos Settlement Cost Per Resolved Claim						11,300	$ 7,800	$ 3,900
Current asbestos liability						$ 66,000,000
Number of buyout agreements with excess insurer groups	10
Aggregate Value Of Policy Buy Out Agreements	$ 82,500,000
Beginning claims	29,089			32,234			32,234
New claims	675		608			2,434
Settlements	(408)		(273)			(1,011)
Dismissals	(858)		(1,579)			(4,568)
Ending claims	28,498	29,089	30,990	32,234	32,234	29,089		32,234
Gross Settlement And Defense Incurred Costs	$ 26,500,000	$ 14,800,000	$ 14,800,000			$ 88,800,000
Payments for asbestos-related fees and costs, net of insurance recoveries	$ 9,700,000	$ 2,900,000	2,900,000			$ 63,900,000
New York | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims | Claim	18,000
Texas | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims | Claim	100
Mississippi | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims | Claim	300
OHIO | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims | Claim	200
James Nelson | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict																			$ 14,500,000
Court Judgment Against All Parties Held Responsible																		$ 4,000,000
Additional Judgment Interest																		$ 10,000
Share Of Responsibility Of Verdict																			9.09%
Thomas Amato [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict																	$ 2,500,000
Share Of Responsibility Of Verdict																	10.00%
PaidJuryVerdict			$ 300,000
Frank Vincinguerra [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict																	$ 2,300,000
Share Of Responsibility Of Verdict																	20.00%
PaidJuryVerdict					$ 600,000
Ivo Peraica | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment																$ 10,600,000
Court_Reduced_Verdict																18,000,000
Paid Judgment Pursuant to Appeal				$ 2,700,000
Jury Verdict Total																$ 35,000,000
Reduced Damages										$ 4,250,000
CourtJudgmentIncludingSetoffs										1,940,000
Richard DeLisle [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict															$ 8,000,000
Court Judgment															$ 1,300,000
Share Of Responsibility Of Verdict															16.00%
Ivan Sweberg [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment														$ 5,300,000
Paid Judgment Pursuant to Appeal				$ 5,700,000
Jury Verdict Total														15,000,000
Reduced Damages										9,500,000
CourtJudgmentIncludingSetoffs										4,730,000
Selwyn Hackshaw [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment														3,100,000
Court_Reduced_Verdict														6,000,000
Jury Verdict Total														$ 10,000,000
Reduced Damages										3,000,000
CourtJudgmentIncludingSetoffs										$ 0
James Poage [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment													$ 10,800,000
compensatory_damages													1,500,000
Additional Damages													$ 10,000,000
Valent Rabovsky [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment											$ 400,000
Share Of Responsibility Of Verdict												30.00%
Jury Verdict Total												$ 1,085,000
George Coulbourn [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment											$ 6,800,000
Share Of Responsibility Of Verdict											20.00%
Jury Verdict Total											$ 9,000,000
Additional Damages											$ 5,000,000
Geoffrey_Anisansel [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict Total									$ 20,000,000