Employee Retirement Plans (Changes In Benefit Obligation And Funded Status Of Employee Retirement Plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Change In Benefit Obligation And Funded Status [Line Items]
Fair value of plan assets at end of year	$ 2,975	$ 2,770
Fair value of plan assets	2,975	2,770
Pension Benefits [Member]
Schedule Of Change In Benefit Obligation And Funded Status [Line Items]
Benefit obligation at beginning of year	3,224	3,008
Service cost	62	53	46
Interest cost	154	153	157
Plan participants' contributions	1	1
Amendments	3	3
Actuarial loss (gain)	409	175
Other	5	3
Benefits paid	(239)	(171)
Foreign currency translation	11	(1)
Benefit obligation at end of year	3,630	3,224	3,008
Fair value of plan assets at beginning of year	2,770	2,690
Actual gain on plan assets	309	232
Employer contributions	122	18
Foreign currency translation	12
Fair value of plan assets at end of year	2,975	2,770	2,690
Fair value of plan assets	2,975	2,770	2,690
Benefit obligations	(3,630)	(3,224)	(3,008)
Funded status of plans	(655)	(454)
Noncurrent asset	14
Current liability	(31)	(11)
Noncurrent liability	(638)	(443)
Recognized liability	(655)	(454)
Net actuarial loss	1,205	1,019
Prior service cost (credit)	25	29
Amount recognized at end of year	1,230	1,048
Postretirement Benefits [Member]
Schedule Of Change In Benefit Obligation And Funded Status [Line Items]
Benefit obligation at beginning of year	957	976
Service cost	13	13	12
Interest cost	45	49	50
Plan participants' contributions	12	12
Actuarial loss (gain)	20	(31)
Other	1
Benefits paid	(66)	(67)
Medicare subsidy received	5	5
Benefit obligation at end of year	987	957	976
Benefit obligations	(987)	(957)	(976)
Funded status of plans	(987)	(957)
Current liability	(57)	(60)
Noncurrent liability	(930)	(897)
Recognized liability	(987)	(957)
Net actuarial loss	274	269
Prior service cost (credit)	(29)	(35)
Amount recognized at end of year	$ 245	$ 234