Derivatives (Schedule of Price Risk Derivatives) (Details)	Jun. 30, 2013
Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	9,687,000
Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,983,000
Year One [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	4,449,000
Year One [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	723,000
Year Two [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	4,458,000
Year Two [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,260,000
Year Three [Member] | Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	780,000
Year Three [Member] | Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held