Employee Retirement Plans (Summary Of The Components Of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Benefits [Member]
Components Of Net Periodic Benefit Expense [Line Items]
Service cost	$ 15	$ 13	$ 30	$ 27
Interest cost	38	39	76	77
Expected return on plan assets	(40)	(40)	(80)	(81)
Amortization of net loss	18	19	35	37
Amortization of prior service cost	1	2	2	4
Total pension and postretirement benefit expense	32	33	63	64
Postretirement Benefits [Member]
Components Of Net Periodic Benefit Expense [Line Items]
Service cost	3	4	6	8
Interest cost	11	12	22	24
Amortization of net loss	4	4	8	9
Amortization of prior service cost	(1)	(2)	(2)	(3)
Total pension and postretirement benefit expense	$ 17	$ 18	$ 34	$ 38