Retirement Plans and Other Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Defined Pension and Other Postretirement Benefit Costs
Amount of pension and other postretirement benefit costs deferred	$ 9	$ 3
Pension Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period	16	16
Interest cost on benefit obligation	30	31
Expected return on plan assets	(35)	(33)
Amortization of net actuarial loss	11	6
Net periodic benefit cost	22	20
Portion of cost charged to expense	6	8
Contributions
Expected contributions in 2012	65
Expected contributions in 2013	160
Expected contributions in 2014	175
Other Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period	7	6
Interest cost on benefit obligation	12	12
Expected return on plan assets	(11)	(10)
Amortization of net actuarial loss	6	3
Net periodic benefit cost	14	11
Portion of cost charged to expense	3	4
Contributions
Expected contributions in 2012	20
Expected contributions in 2013	20
Expected contributions in 2014	$ 20