Commitments and Contingencies (Schedule Of Activity Related To Asbestos Claim) (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) Claim	Mar. 31, 2017	Dec. 31, 2017
Loss Contingencies [Line Items]
Airplane Operating Lease Period Years	7
Fair Value Of Residual Value Guarantee | $	$ 11.1
Fair Value Of Residual Value Guarantee, Fair Value of Operating Lease Asset Threshold | $	$ 14.4
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Beginning claims	32,234	36,052	36,052
New claims	608	818	2,819
Settlements	(273)	(301)	(1,038)
Dismissals	(1,579)	(1,009)	(5,599)
Ending claims	30,990	35,560	32,234
New York | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	18,200
Texas | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	500
Mississippi | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	400
OHIO | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	200