Commitments and Contingencies (Schedule Of Settlement And Defense Costs) (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) Claim	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Document Period End Date	Mar. 31, 2018
Pre-tax cash payments	$ 2,900,000	$ 14,700,000
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Asbestos Cumulative Claims Resolved | Claim	132,000
Loss Contingency, Pending Claims, Number	30,990	35,560	32,234	36,052
Settlement / indemnity costs incurred (1)	$ 8,300,000	$ 18,500,000	$ 51,800,000
Defense costs incurred (1)	6,500,000	9,400,000	36,500,000
Gross Settlement And Defense Incurred Costs	14,800,000	28,000,000	88,300,000
Settlement / indemnity payments	4,600,000	14,100,000	51,700,000
Defense payments	5,000,000	7,900,000	38,900,000
Insurance receipts	(6,700,000)	(7,300,000)	(28,100,000)
Pre-tax cash payments	2,900,000	$ 14,700,000	62,500,000
Cumulative Related Settlement Cost Incurred Before Insurance Recoveries	540,000,000
Cumulative Asbestos Settlement Cost Per Resolved Claim	$ 4,100
Asbestos Settlement Cost Per Resolved Claim			$ 7,800	$ 3,900	$ 3,100