Components of Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension benefits
Components of net periodic cost
Service cost	$ 37	$ 38	$ 113	$ 113
Interest cost	81	80	242	240
Expected return on plan assets	(92)	(83)	(276)	(248)
Amortization of prior service credit		(1)	(1)	(2)
Amortization of net actuarial loss (gain)	39	40	116	119
Settlement loss	9	13	26	39
Net periodic cost	74	87	220	261
Postretirement benefits
Components of net periodic cost
Service cost	2	3	8	9
Interest cost	9	10	27	30
Amortization of prior service credit	(6)	(6)	(17)	(17)
Amortization of net actuarial loss (gain)	(7)	(5)	(22)	(16)
Settlement loss	1		1
Net periodic cost	$ (1)	$ 2	$ (3)	$ 6