Derivatives (Schedule of Price Risk Derivatives) (Details)	Mar. 31, 2014 T
Coal sales [Member]
Derivative [Line Items]
Derivatives Held	5,371,000
Coal purchases [Member]
Derivative [Line Items]
Derivatives Held	1,778,000
Year One [Member] | Coal sales [Member]
Derivative [Line Items]
Derivatives Held	3,991,000
Year One [Member] | Coal purchases [Member]
Derivative [Line Items]
Derivatives Held	1,778,000
Year Two [Member] | Coal sales [Member]
Derivative [Line Items]
Derivatives Held	1,380,000
Year Two [Member] | Coal purchases [Member]
Derivative [Line Items]
Derivatives Held	0