Segment Information (Schedule Of Unallocated Items and Eliminations) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Share-based plans									$ (190)	$ (189)	$ (195)
Deferred compensation									(46)	(63)	(44)
Amortization of previously capitalized interest									(170)	(158)	(102)
Total	$ 2,183	$ 2,282	$ (419)	$ 1,788	$ 1,161	$ 2,580	$ 1,683	$ 2,019	5,834	7,443	7,473
Pension [Member]
Segment Reporting Information [Line Items]
Pension and Postretirement									(1,979)	(2,366)	(3,215)
Postretirement [Member]
Segment Reporting Information [Line Items]
Pension and Postretirement									(274)	(288)	(287)
Unallocated Items And Eliminations [Member]
Segment Reporting Information [Line Items]
Share-based plans									(66)	(76)	(67)
Deferred compensation									(46)	(63)	(44)
Amortization of previously capitalized interest									(94)	(90)	(72)
Eliminations and other unallocated items									(527)	(511)	(593)
Operating Loss Excluding Unallocated Pension and Postretirement Adjustments									(733)	(740)	(776)
Pension and Postretirement									370	(298)	(1,387)
Total									(363)	(1,038)	(2,163)
Unallocated Items And Eliminations [Member] | Pension [Member]
Segment Reporting Information [Line Items]
Pension and Postretirement									217	(421)	(1,469)
Unallocated Items And Eliminations [Member] | Postretirement [Member]
Segment Reporting Information [Line Items]
Pension and Postretirement									$ 153	$ 123	$ 82