Retirement Plans (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Net periodic benefit cost components
Service cost	$ 18	$ 17	$ 17
Interest cost	56	56	56
Expected return on plan assets	(73)	(68)	(61)
Amortization of unrecognized net loss (gain)	8	7	15
Amortization of unrecognized prior service cost	4	5	5
Net periodic benefit cost	13	17	32
Other Postretirement Benefits [Member]
Net periodic benefit cost components
Service cost	4	4	4
Interest cost	10	12	12
Expected return on plan assets	0
Amortization of unrecognized net loss (gain)	0	(1)	(1)
Amortization of unrecognized prior service cost	(1)	(1)	(1)
Net periodic benefit cost	$ 13	$ 14	$ 14