Income Taxes (Schedule Of Reconciliation Of U.S. Federal Statutory Tax Rate To Our Effective Income Tax Rate) (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Dec. 31, 2017	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Examination [Line Items]
U.S. federal statutory tax				21.00%	35.00%	35.00%	35.00%
Impact of Tax Cuts and Jobs Act(1)	[1]				(10.50%)
Tax basis adjustment(2)	[2]					(7.90%)
Federal audit settlements(3)	[3]					(3.20%)
Excess tax benefits(4)	[4]				(2.10%)	(1.90%)
Research and development credits					(1.60%)	(5.20%)	(3.40%)
U.S. manufacturing activity tax benefit					(1.30%)	(3.80%)	(2.90%)
Tax on non-US activities					(0.90%)	(0.50%)	(0.60%)
Other provision adjustments					(0.20%)	(0.40%)	(0.40%)
Effective income tax rate					18.40%	12.10%	27.70%
Effective Income Tax Rate Reconciliation, Impact of tax reform legislation, Amount		$ 1,051
Incremental tax benefit related to tax basis adjustment			$ 440
Excess tax benefits related to employee share-based payments					$ 207	$ 105
Tax Year 2011-2012 [Member]
Income Tax Examination [Line Items]
Tax benefit related to settlement of federal tax audit			$ (177)
Reduction in Taxes [Member]
Income Tax Examination [Line Items]
Effective Income Tax Rate Reconciliation, Impact of tax reform legislation, Amount					1,210
Foreign Tax Authority [Member] | Reduction in Taxes [Member]
Income Tax Examination [Line Items]
Effective Income Tax Rate Reconciliation, Impact of tax reform legislation, Amount					$ (159)

[1] Of the deferred tax asset for net operating loss and credit carryovers, $278 expires on or before December 31, 2036 and $21 may be carried over indefinitely.

[2] In the third quarter of 2016, we recorded incremental tax benefits of $440 related to the application of a 2012 Federal Court of Claims decision which held that the tax basis in certain assets could be increased (tax basis adjustment).

[3] In the third quarter of 2016, a tax benefit of $177 was recorded as a result of the settlement of the 2011-2012 federal tax audit.

[4] In 2017 and 2016, we recorded excess tax benefits related to employee share-based payments of $207 and $105.