Commitments and Contingencies (Asbestos Liability) (Detail)	3 Months Ended				12 Months Ended
	Mar. 31, 2018 USD ($) Claim	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 06, 2016 USD ($)	Sep. 30, 2016 USD ($)	Apr. 22, 2016 USD ($)	Feb. 09, 2016 USD ($)	Jul. 02, 2015 USD ($)	Jun. 16, 2014 USD ($)	Sep. 17, 2013 USD ($)	Jul. 31, 2013 USD ($)	Mar. 01, 2013 USD ($)	Feb. 25, 2013 USD ($)	Oct. 23, 2012 USD ($)	Aug. 17, 2011 USD ($)	Feb. 23, 2011 USD ($)	Mar. 23, 2010 USD ($)
Loss Contingencies [Line Items]
Payments for asbestos-related fees and costs, net of insurance recoveries	$ 2,900,000		$ 14,700,000
Current portion of total estimated liability	$ 85,000,000				$ 85,000,000
Airplane Operating Lease Period Years	7
Fair Value Of Residual Value Guarantee	$ 11,100,000
Fair Value Of Residual Value Guarantee, Fair Value of Operating Lease Asset Threshold	$ 14,400,000
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims	30,990		35,560	36,052	32,234	36,052
Payments for asbestos-related fees and costs, net of insurance recoveries	$ 2,900,000		$ 14,700,000		$ 62,500,000
Cumulative claims resolved | Claim	132,000
Settlement cost	$ 540,000,000
Average settlement cost per resolved claim					7,800	$ 3,900	$ 3,100
Cumulative average settlement cost per resolved claim	4,100
Estimated payments to current and future claimants	36,000,000,000
Additional liability				$ 227,000,000
Liability for claims	596,000,000			$ 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	$ 85,000,000
Number of coverage in place agreements with excess insurer groups	11
Number of buyout agreements with excess insurer groups	10
Aggregate value of policy buyout agreements	$ 82,500,000
Forecasted percentage of liability that would be reimbursed by insurers				21.00%		21.00%
Insurance reimbursement asset	108,000,000			$ 143,000,000		$ 143,000,000
Gross Settlement And Defense Incurred Costs	$ 14,800,000		28,000,000		$ 88,300,000
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%
Ronald Dummitt | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court written decision																			$ 8,000,000
Court Judgment																			4,900,000
courtjudgmentwithinterest									$ 6,600,000
Jury Verdict																			$ 32,000,000
Jury verdict percentage of responsibility.																			99.00%
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%
Gerald Suttner | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment																		$ 100,000
courtjudgmentwithinterest				$ 200,000		$ 200,000
Share Of Responsibility Of Verdict																		4.00%
Plaintiff's Damages																		$ 3,000,000
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
Holdsworth [Member] | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Court Judgment															$ 1,700,000
Motion to enter judgment															1,000,000
Jury Verdict Total															$ 3,100,000
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
Court_Reduced_Verdict													10,000,000
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]
Court Judgment										6,800,000
Jury Verdict Total										9,000,000
Court Reduced damages										$ 5,000,000
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	18,200
Mississippi | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	400
Texas | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	500
Ohio | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Pending claims | Claim	200