Commitments and Contingencies (Schedule Of Activity Related To Asbestos Claim) (Detail) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($) Claim	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018 USD ($) Claim	Jun. 30, 2017	Dec. 31, 2017
Loss Contingencies [Line Items]
Airplane Operating Lease Period Years				7
Fair Value Of Residual Value Guarantee | $	$ 11.1			$ 11.1
Fair Value Of Residual Value Guarantee, Fair Value of Operating Lease Asset Threshold | $	$ 14.4			$ 14.4
Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Beginning claims	30,990	35,560	36,052	32,234	36,052	36,052
New claims	620	684		1,228	1,502	2,819
Settlements	(332)	(327)		(605)	(628)	(1,038)
Dismissals	(1,358)	(3,937)		(2,937)	(4,946)	(5,599)
Ending claims	29,920	31,980	35,560	29,920	31,980	32,234
New York | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	18,000			18,000
Texas | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	400			400
Mississippi | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	400			400
OHIO | Asbestos Commitments and Contingencies
Loss Contingencies [Line Items]
Ending claims	200			200