Retirement Plans (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Qualified Plan [Member]
Underfunded Accumulated Benefit Obligation [Abstract]
Projected benefit obligation		3,165	2,741
Accumulated benefit obligation - pension plans with accumulated benefit obligations in excess of the fair value of the plan assets		(3,050)	(2,663)
Fair value of plan assets		2,505	2,385
Underfunded accumulated benefit obligation		(545)	(278)
Pension Non-qualified Plan [Member]
Underfunded Accumulated Benefit Obligation [Abstract]
Projected benefit obligation		284	257
Pension [Member]
Underfunded Accumulated Benefit Obligation [Abstract]
Accumulated benefit obligation - pension plans with accumulated benefit obligations in excess of the fair value of the plan assets		3,000	2,700
Weighted-Average Actuarial Assumptions Used To Determine Benefit Obligations [Abstract]
Discount rate - benefit obligations		4.54%	5.35%
Salary increase - benefit obligations		4.60%	3.36%
OPEB [Member]
Weighted-Average Actuarial Assumptions Used To Determine Benefit Obligations [Abstract]
Discount rate - benefit obligations		4.36%	5.01%
Health care cost trend rate (employees under 65)		6.91%	7.07%
Ultimate health care cost trend rate	4.50%	4.50%	4.50%	4.50%
Year ultimate trend rate reached	2028	2028	2028	2028