Net Periodic Benefit Cost (Detail) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension Plans, Defined Benefit
Service cost	$ 17	$ 18	$ 35	$ 35
Interest cost	32	32	64	64
Expected return on plan assets	(47)	(46)	(94)	(91)
Amortization of prior service cost	(4)	(3)	(9)	(6)
Recognized net actuarial loss	11	15	21	30
Net periodic benefit cost	9	16	17	32
Other Postretirement Benefit Plans, Defined Benefit
Interest cost	2	2	5	5
Expected return on plan assets	(2)	(2)	(4)	(4)
Recognized net actuarial loss		1		1
Net periodic benefit cost		$ 1	$ 1	$ 2