Commitments And Contingencies (Asbestos Claims Activity) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) claim	Dec. 31, 2020 USD ($) claim	Dec. 31, 2019 USD ($) claim	Dec. 31, 2018 USD ($) claim	Apr. 22, 2016 USD ($)	Jul. 02, 2015 USD ($)	Sep. 17, 2013 USD ($)	Aug. 21, 2012 USD ($)	Feb. 23, 2011 USD ($)	Mar. 23, 2010 USD ($)
Activity Related to Asbestos Claims [Roll Forward]
Payments Or Receipts For Asbestos Related Fees And Costs Net Of Insurance Recoveries		$ 31,100	$ 41,500	$ 63,900
Asbestos Commitments And Contingencies [Member]
Activity Related to Asbestos Claims [Roll Forward]
Beginning claims | claim	29,056	29,056	29,089	32,234
New claims | claim		2,620	2,848	2,434
Settlements | claim		(885)	(983)	(1,011)
Dismissals | claim		(1,653)	(1,898)	(4,568)
Ending claims | claim		29,138	29,056	29,089
Gross Settlement And Defense Incurred Costs		$ 50,900	$ 66,200	$ 88,800
Payments Or Receipts For Asbestos Related Fees And Costs Net Of Insurance Recoveries		$ 31,100	$ 41,500	$ 63,900
Increase In Total Asbestos Liability	$ 255,000
Asbestos Commitments And Contingencies [Member] | NEW YORK
Activity Related to Asbestos Claims [Roll Forward]
Ending claims | claim		18,000
us-gaap_LossContingencyPendingClaimsNumber (nonmalignancy) | claim		16,000
James Nelson [Member] | Asbestos Commitments And Contingencies [Member]
Loss Contingencies [Line Items]
Jury Verdict										$ 14,500
Activity Related to Asbestos Claims [Roll Forward]
Court Judgment Against All Parties Held Responsible									$ 4,000
Additional Judgment Interest									$ 10
Richard DeLisle [Member] | Asbestos Commitments And Contingencies [Member]
Loss Contingencies [Line Items]
Jury Verdict							$ 8,000
Activity Related to Asbestos Claims [Roll Forward]
Court Judgment							$ 1,300
Share Of Responsibility Of Verdict							16.00%
James Poage [Member] | Asbestos Commitments And Contingencies [Member]
Activity Related to Asbestos Claims [Roll Forward]
Court Judgment						$ 10,800
compensatory_damages						1,500
Additional Damages						$ 10,000
George Coulbourn [Member] | Asbestos Commitments And Contingencies [Member]
Activity Related to Asbestos Claims [Roll Forward]
Jury Verdict Total					$ 9,000
Court Judgment					$ 6,800
Share Of Responsibility Of Verdict					20.00%
Additional Damages					$ 5,000
Ronald Dummitt [Member] | Asbestos Commitments And Contingencies [Member]
Activity Related to Asbestos Claims [Roll Forward]
Court Judgment								$ 4,900