Asset Impairment and Mine Closure Costs (Tables)

12 Months Ended

Dec. 31, 2012

Asset Impairment and Mine Closure Costs [Abstract]

Details of Impairment of Long-Lived Assets Held and Used by Asset [Table Text Block]

	Reportable Segment
	Australian Mining		Western U.S. Mining		Midwestern U.S. Mining		Corporate and Other		Consolidated
	(Dollars in millions)
Charges related to mine closures:
Impairment of long-lived assets	$	—	$	—	$	26.9	$	—	$	26.9
Acceleration of asset retirement obligations	—		—		7.1		—		7.1
Employee termination benefits	—		—		6.7		—		6.7
Other	—		—		4.3		—		4.3
Other asset impairment charges:
Long-lived assets held and used	806.7		—		—		—		806.7
Marketable securities	—		—		—		35.5		35.5
Cost method investments	—		—		—		39.4		39.4
Other	—		2.4		—		—		2.4
Total	$	806.7	$	2.4	$	45.0	$	74.9	$	929.0