Commitments and Contingencies (Asbestos Liability) (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 ($)	Dec. 31, 2018 USD ($) Claim	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]
Payments for asbestos-related fees and costs, net of insurance recoveries	$ 9,700,000	$ 2,900,000
Current portion of total estimated liability	$ 66,000,000					$ 66,000,000
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims	28,498	29,089	30,990	32,234	32,234	29,089		32,234
Payments for asbestos-related fees and costs, net of insurance recoveries	$ 9,700,000	$ 2,900,000	$ 2,900,000			$ 63,900,000
Cumulative claims resolved | Claim						137,000
Settlement cost						$ 620,000,000
Average settlement cost per resolved claim						11,300	$ 7,800	$ 3,900
Cumulative average settlement cost per resolved claim						4,500
Estimated payments to current and future claimants						36,000,000,000
Additional liability					$ 227,000,000
Liability for claims	$ 504,000,000				$ 696,000,000			$ 696,000,000
Percentage Of Asbestos Liability Attributable To Settlement And Denfese Costs For Future Claims					80.00%			80.00%
Current portion of total estimated liability						66,000,000
Number of buyout agreements with excess insurer groups	10
Aggregate value of policy buyout agreements	$ 82,500,000
Estimated Percentage Of Insurance Which Covers Asbestos Costs					21.00%			21.00%
Insurance reimbursement asset	88,000,000				$ 143,000,000			$ 143,000,000
Gross Settlement And Defense Incurred Costs	$ 26,500,000	$ 14,800,000	14,800,000			$ 88,800,000
Mesothelioma Claims Percentage Pending Asbestos Claims					10.00%			10.00%
Mesothelioma Claims Percentage Aggregate Settlement Defense Costs					90.00%			90.00%
Frank Paasch | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict																	$ 2,500,000
PaidJuryVerdict			$ 300,000
Share Of Responsibility Of Verdict																	10.00%
James Nelson | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict																			$ 14,500,000
Share Of Responsibility Of Verdict																			9.09%
Court judgment against all parties held responsible																		$ 4,000,000
Additional interest on the compensation awarded																		$ 10,000
Larry Bell | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Share Of Responsibility Of Verdict																			5.00%
Frank Vincinguerra | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict																	$ 2,300,000
PaidJuryVerdict					$ 600,000
Share Of Responsibility Of Verdict																	20.00%
Ivo Peraica | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment																$ 10,600,000
Reduced Damages										$ 4,250,000
CourtJudgmentIncludingSetoffs										1,940,000
Paid Judgment Pursuant to Appeal				$ 2,700,000
Jury Verdict Total																35,000,000
Court_Reduced_Verdict																$ 18,000,000
Richard DeLisle [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment															$ 1,300,000
Jury Verdict															$ 8,000,000
Share Of Responsibility Of Verdict															16.00%
Ivan Sweberg [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment														$ 5,300,000
Reduced Damages										9,500,000
CourtJudgmentIncludingSetoffs										4,730,000
Paid Judgment Pursuant to Appeal				$ 5,700,000
Jury Verdict Total														15,000,000
Selwyn Hackshaw [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment														3,100,000
Reduced Damages										3,000,000
CourtJudgmentIncludingSetoffs										$ 0
Jury Verdict Total														10,000,000
Court_Reduced_Verdict														$ 6,000,000
James Poage [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Compensatory Damages													$ 1,500,000
Additional Damages													10,000,000
Court Judgment													$ 10,800,000
Valent Rabovsky [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment											$ 400,000
Jury Verdict Total												$ 1,085,000
Share Of Responsibility Of Verdict												30.00%
George Coulbourn [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Additional Damages											5,000,000
Court Judgment											6,800,000
Jury Verdict Total											$ 9,000,000
Share Of Responsibility Of Verdict											20.00%
Geoffrey_Anisansel [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Jury Verdict Total									$ 20,000,000
New York | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	18,000
Mississippi | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	300
Texas | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	100
Ohio | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	200