Pension and Other Postretirement Benefits (Details) (Pension Plans [Member], 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 [Member]
Components of pension expense for the defined benefit pension plan
Service cost-benefits earned during the period	$ 4	$ 4	$ 7	$ 8
Interest cost on projected benefit obligation	18	19	35	37
Expected return on assets	(23)	(21)	(44)	(41)
Recognized losses	8	8	19	18
Amortization of prior service cost	(2)	(1)	(3)	(2)
Net periodic cost	$ 5	$ 9	$ 14	$ 20