Commitments and Contingencies (Schedule Of Settlement And Defense Costs) (Detail)	3 Months Ended				12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($) Claim	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2017
Loss Contingencies [Line Items]
Document Period End Date	Mar. 31, 2019
Pre-tax cash payments	$ 9,700,000	$ 2,900,000
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Estimated Percentage Of Insurance Which Covers Asbestos Costs				21.00%			21.00%
Asbestos Cumulative Claims Resolved | Claim					137,000
Loss Contingency, Pending Claims, Number	28,498	29,089	30,990	32,234	29,089		32,234	32,234
Settlement / indemnity costs incurred (1)	$ 21,400,000		$ 8,300,000		$ 63,000,000
Defense costs incurred (1)	5,100,000		6,500,000		25,800,000
Gross Settlement And Defense Incurred Costs	26,500,000	$ 14,800,000	14,800,000		88,800,000
Settlement / indemnity payments	8,800,000		4,600,000		61,500,000
Defense payments	4,000,000		5,000,000		26,500,000
Insurance receipts	(3,100,000)		(6,700,000)		(24,100,000)
Pre-tax cash payments	9,700,000	$ 2,900,000	$ 2,900,000		63,900,000
Cumulative Related Settlement Cost Incurred Before Insurance Recoveries					620,000,000
Cumulative Asbestos Settlement Cost Per Resolved Claim					4,500
Asbestos Settlement Cost Per Resolved Claim					11,300	$ 7,800	$ 3,900
Estimated Funds Available From Post Bankruptcy Trusts To Pay Current And Future Claimants					$ 36,000,000,000
Increase In Total Asbestos Liability				$ 227,000,000
Mesothelioma Claims Percentage Pending Asbestos Claims				10.00%			10.00%
Mesothelioma Claims Percentage Aggregate Settlement Defense Costs				90.00%			90.00%
Insurance Receivable Asbestos	$ 88,000,000			$ 143,000,000			$ 143,000,000