Benefit Plans, Pension and Other Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Benefit Plans [Abstract]
Consecutive calendar months of highest compensation used to calculate employee benefits	60
Change in Plan Assets
Fair Value of Plan Assets, Beginning Balance	$ 206
Fair Value of Plan Assets, Ending Balance	219		206
Other Changes Recognized in AOCL
Total Recognized in AOCL	(17)		0		(2)
Additional disclosures for the retirement and restoration plans [Abstract]
Accumulated Benefit Obligation	267		230
Information for Pension Plans With Projected Benefit Obligations in Excess of Plan Assets
Projected Benefit Obligation	293		262
Fair Value of Plan Assets	219		206
Information for Pension Plans With Accumulated Benefit Obligations in Excess of Plan Assets
Accumulated Benefit Obligation	267		37
Fair Value of Plan Assets	219		0
Target Asset Allocations [Abstract]
Target asset allocation, equity investments (in hundredths)	60.00%		70.00%
Target asset allocation, fixed income investments (in hundredths)	40.00%		30.00%
Target asset allocations, Total (in hundredths)	100.00%		100.00%
Acceptable degree of variation in the plan's asset allocation	plus or minus 10%
Average rate per annum over the life of the plan to calculate net periodic benefit cost (in hundredths)	7.25%
Average rate per annum over the life of the plan to calculate per periodic benefit cost in 2012 (in hundredths)	6.50%
Effect of one percentage point decrease in the discount rate on net periodic benefit cost	2
Effect of one percentage point increase in the discount rate on net periodic benefit cost	3
Assumed health care cost trend rates [Abstract]
Health care cost trend rate assumed for next year (in hundredths)	7.65%		7.83%
Ultimate health care cost trend rate (in hundredths)	4.50%		4.50%
Year rate reaches ultimate trend rate	2030		2030
Effect of one percentage point increase on total service and interest cost components for the current year	0
Effect of one percentage point decrease on total service and interest cost components for the current year	0
Effect of one percentage point increase on year-end postretirement benefit obligation	2
Effect of one percentage point decrease on year-end postretirement benefit obligation	(1)
Actual Plan Asset Allocations [Abstract]
Equity securities (in hundredths)	65.00%		73.00%
Fixed income (in hundredths)	35.00%		27.00%
Total (in hundredths)	100.00%		100.00%
Effect of one percentage point change in the expected return on plan assets on net periodic benefit cost	2
Term over which market-related valuation recognizes investment gains or losses from the year in which they occur (in years)	5
Cumulative asset gains (losses) remaining to be recognized in the calculation of the market-related value of assets	(10)
Retirement and restoration plans [Member]
Change in Benefit Obligation
Benefit Obligation, Beginning Balance	262		228
Service Cost	14		14		12
Interest Cost	13		13		11
Employee Contributions	0		0
Benefits Paid	(13)		(12)
Plan Amendments	0	[1]	0	[1]
Actuarial Net (Gains) Losses	17		19
Benefit Obligation, Ending Balance	293		262		228
Change in Plan Assets
Fair Value of Plan Assets, Beginning Balance	206		172
Actual Return on Plan Assets	(1)		23
Employer/Employee Contributions	27		23
Benefits Paid	(13)		(12)
Fair Value of Plan Assets, Ending Balance	219		206		172
Funded Status of Plan
Funded Status at End of Year	(74)		(56)
Net Amount Recognized in Consolidated Balance Sheets	(74)		(56)
Amounts Recognized in Consolidated Balance Sheets Consist of
Current Liabilities	(3)		(3)
Noncurrent Liabilities	(71)		(53)
Net Amount Recognized in Consolidated Balance Sheets	(74)		(56)
Amounts Not Yet Reflected in Net Periodic Benefit Cost and Included in AOCL
Net Prior Service (Cost) Credit, Before Tax	(2)		(3)
Net Gains (Losses), Before Tax	(120)		(93)
AOCL	(122)		(96)
Cumulative Employer Contributions in Excess of Net Periodic Benefit Cost	48		40
Net Amount Recognized in Consolidated Balance Sheets	(74)		(56)
Components of Net Periodic Benefit Cost
Service Cost	14		14		12
Interest Cost	13		13		11
Expected Return on Plan Assets	(15)		(14)		(14)
Amortization of Prior Service (Credit) Cost	0		0		0
Amortization of Net Loss and Other	6		5		3
Net Periodic Benefit Cost	18		18		12
Other Changes Recognized in AOCL
Prior Service Cost Arising During Period	0		0		0
Net Loss (Gain) Arising During Period	33		10		5
Amortization of Prior Service Credit	0		0		0
Amortization of Net Loss	(6)		(5)		(3)
Total Recognized in AOCL	27		5		2
Expected Amortizations for Next Fiscal Year
Amortization of Net Prior Service Cost (Credit)	0		0		0
Amortization of Net Losses	11		6		5
Weighted-Average Assumptions Used to Determine Benefit Obligations
Discount Rate - Retirement Plans (in hundredths)	4.25%	[2]	5.50%	[2]	6.00%	[2]
Discount Rate - Restoration Plans (in hundredths)	4.25%	[2]	5.25%	[2]	6.00%	[2]
Rate of Compensation Increase - Retirement and Restoration Plans, minimum (in hundredths)	4.00%	[3]	5.00%	[3]	5.00%	[3]
Rate of Compensation Increase - Retirement and Restoration Plans, maximum (in hundredths)	13.00%	[3]	5.00%	[3]	5.00%	[3]
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Costs
Discount Rate - Retirement Plans (in hundredths)	5.50%	[4]	6.00%	[4]	6.00%	[4]
Discount Rate - Restoration Plans (in hundredths)	5.25%	[4]	6.00%	[4]	6.25%	[4]
Expected Long-Term Return on Assets (in hundredths)	7.25%		7.50%		8.00%
Rate of Compensation Increase (in hundredths)	5.00%		5.00%		5.00%
Medical and life plans [Member]
Change in Benefit Obligation
Benefit Obligation, Beginning Balance	24		23
Service Cost	2		2		2
Interest Cost	1		1		1
Employee Contributions	1		1
Benefits Paid	(2)		(1)
Plan Amendments	(6)	[1]	0	[1]
Actuarial Net (Gains) Losses	(2)		(2)
Benefit Obligation, Ending Balance	18		24		23
Change in Plan Assets
Fair Value of Plan Assets, Beginning Balance	0		0
Actual Return on Plan Assets	0		0
Employer/Employee Contributions	2		1
Benefits Paid	(2)		(1)
Fair Value of Plan Assets, Ending Balance	0		0		0
Funded Status of Plan
Funded Status at End of Year	(18)		(24)
Net Amount Recognized in Consolidated Balance Sheets	(18)		(24)
Amounts Recognized in Consolidated Balance Sheets Consist of
Current Liabilities	(1)		(1)
Noncurrent Liabilities	(17)		(23)
Net Amount Recognized in Consolidated Balance Sheets	(18)		(24)
Amounts Not Yet Reflected in Net Periodic Benefit Cost and Included in AOCL
Net Prior Service (Cost) Credit, Before Tax	10		6
Net Gains (Losses), Before Tax	(6)		(9)
AOCL	4		(3)
Cumulative Employer Contributions in Excess of Net Periodic Benefit Cost	(22)		(21)
Net Amount Recognized in Consolidated Balance Sheets	(18)		(24)
Components of Net Periodic Benefit Cost
Service Cost	2		2		2
Interest Cost	1		1		1
Expected Return on Plan Assets	0		0		0
Amortization of Prior Service (Credit) Cost	(1)		(1)		(1)
Amortization of Net Loss and Other	1		1		1
Net Periodic Benefit Cost	3		3		3
Other Changes Recognized in AOCL
Prior Service Cost Arising During Period	(6)		0		(2)
Net Loss (Gain) Arising During Period	(2)		(2)		1
Amortization of Prior Service Credit	1		1		1
Amortization of Net Loss	(1)		(1)		(1)
Total Recognized in AOCL	(8)		(2)		(1)
Expected Amortizations for Next Fiscal Year
Amortization of Net Prior Service Cost (Credit)	(2)		(1)		(1)
Amortization of Net Losses	$ 0		$ 0		$ 1
Weighted-Average Assumptions Used to Determine Benefit Obligations
Discount Rate - Medical and Life Plans (in hundredths)	4.00%	[2]	5.00%	[2]	5.50%	[2]
Rate of Compensation Increase - Retirement and Restoration Plans, minimum (in hundredths)	0.00%	[3]	0.00%	[3]	0.00%	[3]
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Costs
Discount Rate - Medical and Life Plans (in hundredths)	5.00%	[4]	5.50%	[4]	6.25%	[4]
Expected Long-Term Return on Assets (in hundredths)	0.00%		0.00%		0.00%
Rate of Compensation Increase (in hundredths)	0.00%		0.00%		0.00%

[1] Plan amendments relate to an increase in the monthly retiree contributions, changes to annual deductible, co-pays and annual out-of-pocket limit and change to reflect trend on retiree contributions for the medical and life plan.

[2] The discount rates used to determine benefit obligations at December 31, 2010 were 5.50% for the retirement plan and 5.25% for the restoration plan.

[3] The rate of compensation increase used to determine benefit obligations at December 31, 2011 ranged from 4% to 13%. The rate of compensation increase assumption was determined using a historical age based table grouped in five year age intervals.

[4] The discount rates used to determine net periodic benefit costs for the year ended December 31, 2011 were 5.50% for the retirement plan and 5.25% for the restoration plan. The discount rates used to determine net periodic benefit costs for the year ended December 31, 2009 were 6.00% for the retirement plan and 6.25% for the restoration plan.