Retirement Benefits - Estimated Future Pension Benef Pmts (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
US Plans [Member]
Net periodic pension cost (credit) [Line Items]
2014	$ 47.7
2015	48.9
2016	50.0
2017	51.5
2018	53.1
2019 through 2023	287.3
Non-US Plans [Member]
Net periodic pension cost (credit) [Line Items]
2014	14.6
2015	13.7
2016	16.4
2017	19.1
2018	21.3
2019 through 2023	168.8
UMWA Plans Postretirement Medical [Member]
Net periodic pension cost (credit) [Line Items]
2014	31.5
2015	31.9
2016	31.5
2017	31.3
2018	32.9
2019 through 2023	148.6
Pension plan [Member]
Net periodic pension cost (credit) [Line Items]
2014	62.3
2015	62.6
2016	66.4
2017	70.6
2018	74.4
2019 through 2023	456.1
Retirement benefits other than pension [Member]
Net periodic pension cost (credit) [Line Items]
2014	36.5
2015	36.6
2016	35.9
2017	35.4
2018	36.7
2019 through 2023	164.5
Black Lung And Other Plans Postretirement [Member]
Net periodic pension cost (credit) [Line Items]
2014	5.0
2015	4.7
2016	4.4
2017	4.1
2018	3.8
2019 through 2023	$ 15.9