Employee Benefits Schedule of Defined Benefit Plan Disclosures (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
As of January 1				$ 537
Noncurrent asset	(32)	(36)		(32)
Noncurrent liability	(247)	(195)		(247)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	40	97
As of January 1	728	634	550
Service cost	14	12	11
Interest cost on benefit obligation	31	29	28
Participants’ contributions	0	0
Actuarial loss (gain)	77	69
Defined Benefit Plan, Special Termination Benefits	0	0
Benefit payments	(28)	(26)
As of January 1	487	473		537
Unfunded position as of December 31	(191)	(147)
Defined Benefit Plan, Accumulated Benefit Obligation	640	566
Actual return on plan assets	78	14
Company contributions	0	26
Noncurrent asset	0	0
Current liability	0	0
Noncurrent liability	(191)	(147)
Amortization of net actuarial loss	(17)	(8)
Amortization of prior service cost	0	(1)
Total Amounts included in comprehensive income	23	88
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	299	276
Net actuarial loss	298	275
Prior service cost	1	1
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate	4.24%	5.00%
Discount rate used to calculate benefit obligation	5.00%	5.47%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Rate of Compensation Increase	3.65%	3.71%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.71%	3.80%
Long-term rate of return on plan assets	8.25%	8.25%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	8.25%	8.50%
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	5	(4)
As of January 1	84	75	79
Service cost	2	2	2
Interest cost on benefit obligation	3	4	4
Participants’ contributions	2	2
Actuarial loss (gain)	7	(5)
Defined Benefit Plan, Special Termination Benefits	1	0
Benefit payments	(6)	(7)
As of January 1	27	16		28
Unfunded position as of December 31	(56)	(48)
Actual return on plan assets	3	0
Company contributions	2	16
Noncurrent asset	0	0
Current liability	0	0
Noncurrent liability	(56)	(48)
Amortization of net actuarial loss	(1)	(1)
Amortization of prior service cost	(1)	(1)
Total Amounts included in comprehensive income	3	(6)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	22	19
Net actuarial loss	18	15
Prior service cost	4	4
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate	2.77%	3.76%
Discount rate used to calculate benefit obligation		4.02%
Defined Benefit Plan Discount rate - upper range	4.13%
Defined Benefit Plan Cost Discount rate - upper range	4.90%	5.40%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Rate of Compensation Increase	4.58%	4.58%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	4.58%	4.83%
Long-term rate of return on plan assets	6.50%	7.09%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	7.09%	6.44%
Non Qualified Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	2	2
As of January 1	27	27	25
Service cost	0	0	0
Interest cost on benefit obligation	1	1	1
Participants’ contributions	0	0
Actuarial loss (gain)	1	3
Defined Benefit Plan, Special Termination Benefits	0	0
Benefit payments	(2)	(2)
As of January 1	17	19		15
Unfunded position as of December 31	(12)	(10)
Defined Benefit Plan, Accumulated Benefit Obligation	27	27
Actual return on plan assets	0	0
Company contributions	0	0
Noncurrent asset	(15)	(17)
Current liability	(2)	(2)
Noncurrent liability	(25)	(25)
Amortization of net actuarial loss	(1)	(1)
Amortization of prior service cost	0	0
Total Amounts included in comprehensive income	1	1
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	11	10
Net actuarial loss	11	10
Prior service cost	$ 0	$ 0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate	4.24%	5.00%
Discount rate used to calculate benefit obligation		5.47%