Pension And Other Postretirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) (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 Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 7	$ 18	$ 17
Interest cost	27	27	53	53
Expected return on plan assets	(32)	(33)	(66)	(64)
Amortization of prior service cost (benefit)	1	(1)	1	(1)
Amortization of net actuarial loss	18	11	32	24
Net periodic benefit cost	21	11	38	29
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	1	4	3
Interest cost	8	9	17	18
Expected return on plan assets	(4)	(4)	(9)	(9)
Amortization of prior service cost (benefit)	(1)	(1)	(2)	(2)
Amortization of net actuarial loss	2	2	7	6
Termination benefits	1	1	1	1
Net periodic benefit cost	$ 9	$ 8	$ 18	$ 17