Retirement Benefits - Assumptions (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net periodic pension cost (credit) [Line Items]
Discount rate - benefit obligation at year end	5.00%	4.20%	4.60%
US Plans [Member]
Net periodic pension cost (credit) [Line Items]
Discount rate - pension cost	4.20%	4.60%	5.30%
Expected return on assets - Pension cost	8.00%	8.25%	8.75%
Non-US Plans [Member]
Net periodic pension cost (credit) [Line Items]
Discount rate - pension cost	5.30%	5.40%	5.80%
Discount rate - benefit obligation at year end	6.30%	5.30%	5.40%
Expected return on assets - Pension cost	4.64%	4.92%	5.16%
Average rate of increase in salaries - pension cost	3.80%	3.20%	3.30%
Average rate of increase in salaries - benefit obligation at year end	3.90%	3.80%	3.20%
UMWA Plans Postretirement Medical [Member]
Net periodic pension cost (credit) [Line Items]
Discount rate - pension cost	3.90%	4.40%	5.30%
Discount rate - benefit obligation at year end	4.70%	3.90%	4.40%
Black Lung And Other Plans Postretirement [Member]
Net periodic pension cost (credit) [Line Items]
Discount rate - pension cost	3.50%	4.20%	4.80%
Discount rate - benefit obligation at year end	4.40%	3.50%	4.20%
Retirement benefits other than pension [Member]
Net periodic pension cost (credit) [Line Items]
Discount rate - pension cost	3.90%	4.40%	5.20%
Discount rate - benefit obligation at year end	4.70%	3.90%	4.40%
Expected return on assets - Pension cost	8.25%	8.50%	8.75%