Coal Impairment Charges and Discontinued Operations (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended			9 Months Ended			3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Coal Mining Business	Sep. 30, 2014 Coal Mining Business	Jun. 30, 2014 Coal Mining Business	Sep. 30, 2014 Coal Mining Business	Sep. 30, 2014 Coal Mining Business Minimum T	Sep. 30, 2014 Coal Mining Business Maximum T	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Minimum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Maximum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Exit and Disposal Costs Minimum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Exit and Disposal Costs Maximum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Employee Severances Minimum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Employee Severances Maximum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Contract Terminations Minimum	Dec. 31, 2014 Coal Mining Business Scenario, Forecast Contract Terminations Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment	$ 0	$ 0	$ 15.1	$ 0		$ 16.4	$ 97.1
Coal sales price (in dollars per ton)									97	149
Sales volumes (in tons)									1,600,000	1,800,000
Discount rate (as a percent)								14.00%
Pre-tax impairment of goodwill							6.0
Impairment, income tax benefit						6.4	7.6
Asset and goodwill impairment							88.0
Asset and goodwill impairment, tax benefit							44.5
Impairment of retained assets							15.1
Expected costs													10	15	1	2	9	13
Payments for restructuring			0.7								10.0	14.0
Restructuring costs					$ 0.6