Retirement Benefits Plans - Other Postretirement Benefits Plan Assumptions (Details 8) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Effect on total service and interest cost, 1% increase	1
Effect on total service and interest cost, 1% decrease	(1)
Effect on other postretirement liabilities, 1% increase	18
Effect on other postretirement liabilities, 1% decrease	(16)
Other postretirement benefits plans [Member]
Assumptions used to determine benefit obligation at year-end
Discount rate	4.60%	5.20%	5.70%
Health care cost trend rate assumed for next year	7.60%	8.10%	8.30%
Ultimate health care cost trend rate	4.50%	4.50%	4.75%
Year ultimate health care cost trend rate is achieved	2020	2020	2017
Assumptions used to determine expense
Discount rate	5.20%	5.70%	6.30%
Initial health care cost trend rate	8.10%	8.30%	8.25%
Ultimate health care cost trend rate	4.50%	4.75%	4.75%
Year ultimate health care cost trend rate is achieved	2020	2017	2017