Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits [Member]
Net periodic benefit cost components
Service cost	$ 6	$ 4	$ 18	$ 14
Interest cost	14	14	42	42
Expected return on plan assets	(19)	(18)	(57)	(55)
Amortization of net loss	5	2	16	6
Amortization of prior service cost	1	1	3	3
Net periodic benefit cost	7	3	22	10
Other Postretirement Benefits [Member]
Net periodic benefit cost components
Service cost	1	1	4	3
Interest cost	3	3	7	8
Amortization of net loss		(1)		(1)
Net periodic benefit cost	$ 4	$ 3	$ 11	$ 10