Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		12 Months Ended	9 Months Ended	1 Months Ended		9 Months Ended	1 Months Ended	9 Months Ended
	Jun. 30, 2012 day	Jun. 30, 2010 day	Dec. 31, 2008	Sep. 30, 2012 Environmental Matters Walter Coke, Inc. item	May 30, 2012 Securities Class Actions and Shareholder Derivative Actions item	Jan. 31, 2012 Securities Class Actions and Shareholder Derivative Actions item	Sep. 30, 2012 Securities Class Actions and Shareholder Derivative Actions item	Nov. 30, 2009 Securities Class Actions and Shareholder Derivative Actions Western Coal Corp item	Sep. 30, 2012 Securities Class Actions and Shareholder Derivative Actions Western Coal Corp
Commitments and contingencies
Extension period to submit proposed final order (in days)		90
Comment letter period (in days)	30	30
Number of properties that the entity has agreed to remediate				23
Term of corrective measures studies				24 months
Number of properties remediated				16
Benefit of deemed liquidation of entity's homebuilding business			$ 167.0
Number of actions					2
Number of executive directors as defendants						3
Number of complaints							3
Number of non-executive directors as defendants								2
General damages entitled to recover									200
Punitive damages entitled to recover									$ 20