Components of Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension benefits
Components of net periodic cost
Service cost	$ 38	$ 37	$ 76	$ 75
Interest cost	80	80	161	160
Expected return on plan assets	(92)	(82)	(184)	(165)
Amortization of prior service credit	(1)		(1)	(1)
Amortization of net actuarial loss (gain)	39	39	77	79
Settlement loss	8	13	17	26
Net periodic cost	72	87	146	174
Postretirement benefits
Components of net periodic cost
Service cost	3	3	6	6
Interest cost	9	10	18	20
Amortization of prior service credit	(5)	(5)	(11)	(11)
Amortization of net actuarial loss (gain)	(8)	(6)	(15)	(11)
Net periodic cost	$ (1)	$ 2	$ (2)	$ 4