Retirement Plans and Other Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Defined Pension and Other Postretirement Benefit Costs
Amount of pension and other postretirement benefit costs deferred	$ 5	$ 3	$ 14	$ 6
Pension Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period	15	13	32	29
Interest cost on benefit obligation	30	31	60	62
Expected return on plan assets	(35)	(33)	(71)	(67)
Amortization of prior service cost			1	1
Amortization of net actuarial loss	12	7	22	13
Net periodic benefit cost	22	18	44	38
Portion of cost charged to expense	8	7	13	15
Contributions
Expected contributions in 2012	65		65
Expected contributions in 2013	150		150
Expected contributions in 2014	160		160
Contributions paid during the period			15
Other Benefits
Net periodic benefit costs and the portion of these costs charged to expense
Service cost - benefits earned during the period	6	5	14	11
Interest cost on benefit obligation	11	12	23	23
Expected return on plan assets	(11)	(11)	(23)	(21)
Amortization of net actuarial loss	4	4	10	8
Net periodic benefit cost	10	10	24	21
Portion of cost charged to expense	3	4	6	8
Contributions
Expected contributions in 2012	20		20
Expected contributions in 2013	20		20
Expected contributions in 2014	$ 20		$ 20