Retirement Benefits - Retirement Cost (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
US Plans [Member]
Net periodic pension cost (credit) [Line Items]
Service cost	$ 0	$ 0
Interest cost	11.0	11.5
Return on assets - expected	(15.1)	(16.3)
Amortization of (gains) losses	10.0	7.0
Net periodic pension cost (credit)	9.9	2.2
Non-US Plans [Member]
Net periodic pension cost (credit) [Line Items]
Service cost	2.6	2.8
Interest cost	4.1	4.3
Return on assets - expected	(3.0)	(3.1)
Amortization of (gains) losses	1.1	0.8
Net periodic pension cost (credit)	6.0	5.2
UMWA plans [Member]
Net periodic pension cost (credit) [Line Items]
Interest cost	5.6	6.1
Return on assets - expected	(5.3)	(6.4)
Amortization of (gains) losses	5.4	3.7
Net periodic pension cost (credit)	5.7	3.4
Pension plan [Member]
Net periodic pension cost (credit) [Line Items]
Service cost	2.6	2.8
Interest cost	15.1	15.8
Return on assets - expected	(18.1)	(19.4)
Amortization of (gains) losses	11.1	7.8
Net periodic pension cost (credit)	15.9	7.4
Retirement benefits other than pension [Member]
Net periodic pension cost (credit) [Line Items]
Interest cost	6.4	6.8
Return on assets - expected	(5.3)	(6.4)
Amortization of (gains) losses	5.6	3.8
Net periodic pension cost (credit)	$ 7.2	$ 4.7